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	$91.75	8.194%	$99.268	$99.27	$99.25	$99.30
Purchase #2	$74.64	5.429%	$78.6922	$78.69	$78.70	$78.70
Purchase #3	$240.60	12.557%	$270.8121	$270.81	$270.80	$270.80
Purchase #4	$74.95	7.375%	$80.4776	$80.48	$80.50	$80.50
Purchase #5	$178.88	6.522%	$190.5466	$190.55	$190.55	$190.50
Purchase #6	$168.66	6.340%	$179.353	$179.35	$179.35	$179.40
Purchase #7	$206.75	11.104%	$229.7075	$229.71	$229.70	$229.70
7 purchase totals =	$1,036.23		$1,128.8570	$1,128.86	$1,128.85	$1,128.90