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	$73.60	7.282%	$78.9596	$78.96	$78.95	$79.00
Purchase #2	$78.83	13.278%	$89.297	$89.30	$89.30	$89.30
Purchase #3	$223.74	12.219%	$251.0788	$251.08	$251.10	$251.10
Purchase #4	$18.74	3.516%	$19.3989	$19.40	$19.40	$19.40
Purchase #5	$97.70	13.569%	$110.9569	$110.96	$110.95	$111.00
Purchase #6	$197.90	12.364%	$222.3684	$222.37	$222.35	$222.40
Purchase #7	$76.42	13.437%	$86.6886	$86.69	$86.70	$86.70
7 purchase totals =	$766.93		$858.7482	$858.76	$858.75	$858.90