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	$40.94	12.307%	$45.9785	$45.98	$46.00	$46.00
Purchase #2	$141.71	12.396%	$159.2764	$159.28	$159.30	$159.30
Purchase #3	$151.39	3.206%	$156.2436	$156.24	$156.25	$156.20
Purchase #4	$185.49	11.815%	$207.4056	$207.41	$207.40	$207.40
Purchase #5	$157.79	6.572%	$168.16	$168.16	$168.15	$168.20
Purchase #6	$172.50	13.769%	$196.2515	$196.25	$196.25	$196.30
Purchase #7	$172.70	6.745%	$184.3486	$184.35	$184.35	$184.30
7 purchase totals =	$1,022.52		$1,117.6642	$1,117.67	$1,117.70	$1,117.70