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	$85.67	4.271%	$89.329	$89.33	$89.35	$89.30
Purchase #2	$106.52	4.304%	$111.1046	$111.10	$111.10	$111.10
Purchase #3	$243.45	5.862%	$257.721	$257.72	$257.70	$257.70
Purchase #4	$140.35	7.346%	$150.6601	$150.66	$150.65	$150.70
Purchase #5	$39.53	7.814%	$42.6189	$42.62	$42.60	$42.60
Purchase #6	$203.45	9.222%	$222.2122	$222.21	$222.20	$222.20
Purchase #7	$240.97	11.566%	$268.8406	$268.84	$268.85	$268.80
7 purchase totals =	$1,059.94		$1,142.4864	$1,142.48	$1,142.45	$1,142.40