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	$49.33	4.347%	$51.4744	$51.47	$51.45	$51.50
Purchase #2	$178.52	9.822%	$196.0542	$196.05	$196.05	$196.10
Purchase #3	$117.74	5.660%	$124.4041	$124.40	$124.40	$124.40
Purchase #4	$83.85	10.328%	$92.51	$92.51	$92.50	$92.50
Purchase #5	$138.44	13.374%	$156.955	$156.96	$156.95	$157.00
Purchase #6	$48.69	13.268%	$55.1502	$55.15	$55.15	$55.20
Purchase #7	$63.27	3.109%	$65.2371	$65.24	$65.25	$65.20
7 purchase totals =	$679.84		$741.7850	$741.78	$741.75	$741.90