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	$166.71	11.532%	$185.935	$185.94	$185.95	$185.90
Purchase #2	$166.37	4.398%	$173.687	$173.69	$173.70	$173.70
Purchase #3	$206.35	7.655%	$222.1461	$222.15	$222.15	$222.10
Purchase #4	$166.49	3.452%	$172.2372	$172.24	$172.25	$172.20
Purchase #5	$29.42	9.811%	$32.3064	$32.31	$32.30	$32.30
Purchase #6	$243.53	5.265%	$256.3519	$256.35	$256.35	$256.40
Purchase #7	$76.59	3.320%	$79.1328	$79.13	$79.15	$79.10
7 purchase totals =	$1,055.46		$1,121.7964	$1,121.81	$1,121.85	$1,121.70