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	$200.58	5.752%	$212.1174	$212.12	$212.10	$212.10
Purchase #2	$109.95	10.317%	$121.2935	$121.29	$121.30	$121.30
Purchase #3	$220.98	6.515%	$235.3768	$235.38	$235.40	$235.40
Purchase #4	$143.59	6.718%	$153.2364	$153.24	$153.25	$153.20
Purchase #5	$185.52	5.857%	$196.3859	$196.39	$196.40	$196.40
Purchase #6	$22.89	6.344%	$24.3421	$24.34	$24.35	$24.30
Purchase #7	$70.89	3.741%	$73.542	$73.54	$73.55	$73.50
7 purchase totals =	$954.40		$1,016.2941	$1,016.30	$1,016.35	$1,016.20