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	$117.29	4.267%	$122.2948	$122.29	$122.30	$122.30
Purchase #2	$246.57	12.866%	$278.2937	$278.29	$278.30	$278.30
Purchase #3	$203.60	11.118%	$226.2362	$226.24	$226.25	$226.20
Purchase #4	$156.47	9.558%	$171.4254	$171.43	$171.45	$171.40
Purchase #5	$135.97	10.732%	$150.5623	$150.56	$150.55	$150.60
Purchase #6	$67.51	7.717%	$72.7197	$72.72	$72.70	$72.70
Purchase #7	$155.62	12.256%	$174.6928	$174.69	$174.70	$174.70
7 purchase totals =	$1,083.03		$1,196.2249	$1,196.22	$1,196.25	$1,196.20