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	$163.83	10.768%	$181.4712	$181.47	$181.45	$181.50
Purchase #2	$70.90	11.200%	$78.8408	$78.84	$78.85	$78.80
Purchase #3	$20.62	13.791%	$23.4637	$23.46	$23.45	$23.50
Purchase #4	$89.89	6.529%	$95.7589	$95.76	$95.75	$95.80
Purchase #5	$108.25	9.464%	$118.4948	$118.49	$118.50	$118.50
Purchase #6	$53.40	5.211%	$56.1827	$56.18	$56.20	$56.20
Purchase #7	$55.34	13.751%	$62.9498	$62.95	$62.95	$62.90
7 purchase totals =	$562.23		$617.1619	$617.15	$617.15	$617.20