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	$159.29	11.624%	$177.8059	$177.81	$177.80	$177.80
Purchase #2	$70.34	8.511%	$76.3266	$76.33	$76.35	$76.30
Purchase #3	$101.57	9.415%	$111.1328	$111.13	$111.15	$111.10
Purchase #4	$186.87	3.721%	$193.8234	$193.82	$193.80	$193.80
Purchase #5	$156.65	3.580%	$162.2581	$162.26	$162.25	$162.30
Purchase #6	$209.31	9.375%	$228.9328	$228.93	$228.95	$228.90
Purchase #7	$101.92	9.397%	$111.4974	$111.50	$111.50	$111.50
7 purchase totals =	$985.95		$1,061.7770	$1,061.78	$1,061.80	$1,061.70