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	$188.69	6.499%	$200.953	$200.95	$200.95	$201.00
Purchase #2	$77.48	3.783%	$80.4111	$80.41	$80.40	$80.40
Purchase #3	$73.45	7.371%	$78.864	$78.86	$78.85	$78.90
Purchase #4	$178.57	9.386%	$195.3306	$195.33	$195.35	$195.30
Purchase #5	$37.76	9.353%	$41.2917	$41.29	$41.30	$41.30
Purchase #6	$70.87	13.839%	$80.6777	$80.68	$80.70	$80.70
Purchase #7	$184.78	8.248%	$200.0207	$200.02	$200.00	$200.00
7 purchase totals =	$811.60		$877.5488	$877.54	$877.55	$877.60