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	$153.69	7.820%	$165.7086	$165.71	$165.70	$165.70
Purchase #2	$134.95	7.108%	$144.5422	$144.54	$144.55	$144.50
Purchase #3	$27.98	11.253%	$31.1286	$31.13	$31.15	$31.10
Purchase #4	$145.48	7.386%	$156.2252	$156.23	$156.25	$156.20
Purchase #5	$225.86	6.442%	$240.4099	$240.41	$240.40	$240.40
Purchase #6	$53.30	9.674%	$58.4562	$58.46	$58.45	$58.50
Purchase #7	$207.60	13.446%	$235.5139	$235.51	$235.50	$235.50
7 purchase totals =	$948.86		$1,031.9846	$1,031.99	$1,032.00	$1,031.90