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	$142.88	7.737%	$153.9346	$153.93	$153.95	$153.90
Purchase #2	$55.46	6.620%	$59.1315	$59.13	$59.15	$59.10
Purchase #3	$165.67	3.345%	$171.2117	$171.21	$171.20	$171.20
Purchase #4	$248.33	11.466%	$276.8035	$276.80	$276.80	$276.80
Purchase #5	$222.47	9.126%	$242.7726	$242.77	$242.75	$242.80
Purchase #6	$103.25	8.256%	$111.7743	$111.77	$111.75	$111.80
Purchase #7	$76.49	13.540%	$86.8467	$86.85	$86.85	$86.80
7 purchase totals =	$1,014.55		$1,102.4749	$1,102.46	$1,102.45	$1,102.40