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	$50.76	6.503%	$54.0609	$54.06	$54.05	$54.10
Purchase #2	$152.85	8.120%	$165.2614	$165.26	$165.25	$165.30
Purchase #3	$242.57	5.416%	$255.7076	$255.71	$255.70	$255.70
Purchase #4	$163.49	7.447%	$175.6651	$175.67	$175.65	$175.70
Purchase #5	$92.35	8.810%	$100.486	$100.49	$100.50	$100.50
Purchase #6	$229.48	11.393%	$255.6247	$255.62	$255.60	$255.60
Purchase #7	$82.38	3.758%	$85.4758	$85.48	$85.50	$85.50
7 purchase totals =	$1,013.88		$1,092.2815	$1,092.29	$1,092.25	$1,092.40