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	$50.63	3.140%	$52.2198	$52.22	$52.20	$52.20
Purchase #2	$74.96	10.559%	$82.875	$82.88	$82.90	$82.90
Purchase #3	$133.55	13.325%	$151.3455	$151.35	$151.35	$151.30
Purchase #4	$194.64	10.450%	$214.9799	$214.98	$215.00	$215.00
Purchase #5	$49.25	8.655%	$53.5126	$53.51	$53.50	$53.50
Purchase #6	$232.69	4.682%	$243.5845	$243.58	$243.60	$243.60
Purchase #7	$229.56	12.265%	$257.7155	$257.72	$257.70	$257.70
7 purchase totals =	$965.28		$1,056.2328	$1,056.24	$1,056.25	$1,056.20