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	$59.73	11.798%	$66.7769	$66.78	$66.80	$66.80
Purchase #2	$26.60	4.507%	$27.7989	$27.80	$27.80	$27.80
Purchase #3	$41.40	5.761%	$43.7851	$43.79	$43.80	$43.80
Purchase #4	$71.92	6.118%	$76.3201	$76.32	$76.30	$76.30
Purchase #5	$99.37	12.335%	$111.6273	$111.63	$111.65	$111.60
Purchase #6	$25.47	12.170%	$28.5697	$28.57	$28.55	$28.60
Purchase #7	$238.28	13.552%	$270.5717	$270.57	$270.55	$270.60
7 purchase totals =	$562.77		$625.4497	$625.46	$625.45	$625.50