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	$243.55	4.415%	$254.3027	$254.30	$254.30	$254.30
Purchase #2	$44.40	9.706%	$48.7095	$48.71	$48.70	$48.70
Purchase #3	$172.67	3.220%	$178.23	$178.23	$178.25	$178.20
Purchase #4	$102.87	8.554%	$111.6695	$111.67	$111.65	$111.70
Purchase #5	$52.34	13.497%	$59.4043	$59.40	$59.40	$59.40
Purchase #6	$191.97	12.571%	$216.1025	$216.10	$216.10	$216.10
Purchase #7	$215.59	9.155%	$235.3273	$235.33	$235.35	$235.30
7 purchase totals =	$1,023.39		$1,103.7458	$1,103.74	$1,103.75	$1,103.70