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	$223.77	9.833%	$245.7733	$245.77	$245.75	$245.80
Purchase #2	$184.63	8.235%	$199.8343	$199.83	$199.85	$199.80
Purchase #3	$80.71	9.605%	$88.4622	$88.46	$88.45	$88.50
Purchase #4	$138.86	6.609%	$148.0373	$148.04	$148.05	$148.00
Purchase #5	$151.59	9.115%	$165.4074	$165.41	$165.40	$165.40
Purchase #6	$236.39	5.536%	$249.4766	$249.48	$249.50	$249.50
Purchase #7	$89.51	3.501%	$92.6437	$92.64	$92.65	$92.60
7 purchase totals =	$1,105.46		$1,189.6348	$1,189.63	$1,189.65	$1,189.60