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	$104.34	6.462%	$111.0825	$111.08	$111.10	$111.10
Purchase #2	$58.54	3.479%	$60.5766	$60.58	$60.60	$60.60
Purchase #3	$84.78	12.323%	$95.2274	$95.23	$95.25	$95.20
Purchase #4	$192.77	13.853%	$219.4744	$219.47	$219.45	$219.50
Purchase #5	$223.75	11.398%	$249.253	$249.25	$249.25	$249.30
Purchase #6	$53.84	7.326%	$57.7843	$57.78	$57.80	$57.80
Purchase #7	$139.93	7.754%	$150.7802	$150.78	$150.80	$150.80
7 purchase totals =	$857.95		$944.1784	$944.17	$944.25	$944.30