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	$148.67	3.775%	$154.2823	$154.28	$154.30	$154.30
Purchase #2	$86.37	3.557%	$89.4422	$89.44	$89.45	$89.40
Purchase #3	$108.58	6.373%	$115.4998	$115.50	$115.50	$115.50
Purchase #4	$59.47	10.161%	$65.5127	$65.51	$65.50	$65.50
Purchase #5	$140.78	5.551%	$148.5947	$148.59	$148.60	$148.60
Purchase #6	$224.60	4.674%	$235.0978	$235.10	$235.10	$235.10
Purchase #7	$53.68	7.538%	$57.7264	$57.73	$57.75	$57.70
7 purchase totals =	$822.15		$866.1559	$866.15	$866.20	$866.10