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	$41.60	11.725%	$46.4776	$46.48	$46.50	$46.50
Purchase #2	$107.34	3.505%	$111.1023	$111.10	$111.10	$111.10
Purchase #3	$249.69	5.851%	$264.2994	$264.30	$264.30	$264.30
Purchase #4	$105.35	7.815%	$113.5831	$113.58	$113.60	$113.60
Purchase #5	$127.34	10.771%	$141.0558	$141.06	$141.05	$141.10
Purchase #6	$202.65	3.160%	$209.0537	$209.05	$209.05	$209.10
Purchase #7	$72.38	5.294%	$76.2118	$76.21	$76.20	$76.20
7 purchase totals =	$906.35		$961.7837	$961.78	$961.80	$961.90