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	$113.74	5.802%	$120.3392	$120.34	$120.35	$120.30
Purchase #2	$6.44	10.672%	$7.1273	$7.13	$7.15	$7.10
Purchase #3	$40.54	6.414%	$43.1402	$43.14	$43.15	$43.10
Purchase #4	$155.70	5.639%	$164.4799	$164.48	$164.50	$164.50
Purchase #5	$215.95	11.375%	$240.5143	$240.51	$240.50	$240.50
Purchase #6	$107.61	3.615%	$111.5001	$111.50	$111.50	$111.50
Purchase #7	$15.49	4.745%	$16.225	$16.23	$16.25	$16.20
7 purchase totals =	$655.47		$703.3260	$703.33	$703.40	$703.20