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	$70.67	11.873%	$79.0606	$79.06	$79.05	$79.10
Purchase #2	$89.73	8.121%	$97.017	$97.02	$97.00	$97.00
Purchase #3	$64.88	4.692%	$67.9242	$67.92	$67.90	$67.90
Purchase #4	$50.33	4.237%	$52.4625	$52.46	$52.45	$52.50
Purchase #5	$90.89	5.141%	$95.5627	$95.56	$95.55	$95.60
Purchase #6	$32.73	13.663%	$37.2019	$37.20	$37.20	$37.20
Purchase #7	$165.62	10.252%	$182.5994	$182.60	$182.60	$182.60
7 purchase totals =	$564.85		$611.8283	$611.82	$611.75	$611.90