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	$80.31	6.350%	$85.4097	$85.41	$85.40	$85.40
Purchase #2	$145.69	3.187%	$150.3331	$150.33	$150.35	$150.30
Purchase #3	$128.93	9.127%	$140.6974	$140.70	$140.70	$140.70
Purchase #4	$59.29	12.748%	$66.8483	$66.85	$66.85	$66.80
Purchase #5	$12.89	13.809%	$14.67	$14.67	$14.65	$14.70
Purchase #6	$207.73	5.640%	$219.446	$219.45	$219.45	$219.40
Purchase #7	$102.95	8.336%	$111.5319	$111.53	$111.55	$111.50
7 purchase totals =	$737.79		$788.9364	$788.94	$788.95	$788.80