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	$113.86	11.512%	$126.9676	$126.97	$126.95	$127.00
Purchase #2	$121.80	6.281%	$129.4503	$129.45	$129.45	$129.50
Purchase #3	$98.61	13.117%	$111.5447	$111.54	$111.55	$111.50
Purchase #4	$247.50	11.354%	$275.6012	$275.60	$275.60	$275.60
Purchase #5	$50.26	5.373%	$52.9605	$52.96	$52.95	$53.00
Purchase #6	$129.84	5.115%	$136.4813	$136.48	$136.50	$136.50
Purchase #7	$212.69	7.312%	$228.2419	$228.24	$228.25	$228.20
7 purchase totals =	$974.56		$1,061.2475	$1,061.24	$1,061.25	$1,061.30