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	$134.51	5.630%	$142.0829	$142.08	$142.10	$142.10
Purchase #2	$60.46	8.362%	$65.5157	$65.52	$65.50	$65.50
Purchase #3	$23.95	5.853%	$25.3518	$25.35	$25.35	$25.40
Purchase #4	$135.74	12.512%	$152.7238	$152.72	$152.70	$152.70
Purchase #5	$174.32	9.245%	$190.4359	$190.44	$190.45	$190.40
Purchase #6	$209.37	10.579%	$231.5193	$231.52	$231.50	$231.50
Purchase #7	$108.70	7.529%	$116.884	$116.88	$116.90	$116.90
7 purchase totals =	$847.05		$924.5134	$924.51	$924.50	$924.50