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	$68.61	3.452%	$70.9784	$70.98	$71.00	$71.00
Purchase #2	$67.70	5.728%	$71.5779	$71.58	$71.60	$71.60
Purchase #3	$155.94	13.505%	$176.9997	$177.00	$177.00	$177.00
Purchase #4	$134.62	10.326%	$148.5209	$148.52	$148.50	$148.50
Purchase #5	$211.32	12.685%	$238.1259	$238.13	$238.15	$238.10
Purchase #6	$52.77	6.683%	$56.2966	$56.30	$56.30	$56.30
Purchase #7	$225.56	6.731%	$240.7424	$240.74	$240.75	$240.70
7 purchase totals =	$916.52		$1,003.2418	$1,003.25	$1,003.30	$1,003.20