Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$192.76	5.434%	$203.2346	$203.23	$203.25	$203.20
Purchase #2	$114.58	12.430%	$128.8223	$128.82	$128.80	$128.80
Purchase #3	$153.81	7.280%	$165.0074	$165.01	$165.00	$165.00
Purchase #4	$113.57	12.549%	$127.8219	$127.82	$127.80	$127.80
Purchase #5	$192.56	12.311%	$216.2661	$216.27	$216.25	$216.30
Purchase #6	$169.52	6.457%	$180.4659	$180.47	$180.45	$180.50
Purchase #7	$95.51	10.506%	$105.5443	$105.54	$105.55	$105.50
7 purchase totals =	$1,032.31		$1,127.1625	$1,127.16	$1,127.10	$1,127.10