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	$56.42	8.158%	$61.0227	$61.02	$61.00	$61.00
Purchase #2	$183.82	13.814%	$209.2129	$209.21	$209.20	$209.20
Purchase #3	$144.36	7.113%	$154.6283	$154.63	$154.65	$154.60
Purchase #4	$75.32	4.554%	$78.7501	$78.75	$78.75	$78.80
Purchase #5	$166.69	5.689%	$176.173	$176.17	$176.15	$176.20
Purchase #6	$52.39	12.771%	$59.0807	$59.08	$59.10	$59.10
Purchase #7	$114.86	11.626%	$128.2136	$128.21	$128.20	$128.20
7 purchase totals =	$793.86		$867.0813	$867.07	$867.05	$867.10