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	$48.63	7.404%	$52.2306	$52.23	$52.25	$52.20
Purchase #2	$207.52	4.139%	$216.1093	$216.11	$216.10	$216.10
Purchase #3	$156.76	10.113%	$172.6131	$172.61	$172.60	$172.60
Purchase #4	$121.42	10.316%	$133.9457	$133.95	$133.95	$133.90
Purchase #5	$79.94	4.357%	$83.423	$83.42	$83.40	$83.40
Purchase #6	$135.33	12.441%	$152.1664	$152.17	$152.15	$152.20
Purchase #7	$92.35	9.258%	$100.8998	$100.90	$100.90	$100.90
7 purchase totals =	$841.95		$911.3879	$911.39	$911.35	$911.30