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	$79.81	9.279%	$87.2156	$87.22	$87.20	$87.20
Purchase #2	$84.80	7.206%	$90.9107	$90.91	$90.90	$90.90
Purchase #3	$78.61	6.486%	$83.7086	$83.71	$83.70	$83.70
Purchase #4	$57.48	7.458%	$61.7669	$61.77	$61.75	$61.80
Purchase #5	$43.90	3.615%	$45.487	$45.49	$45.50	$45.50
Purchase #6	$25.25	6.290%	$26.8382	$26.84	$26.85	$26.80
Purchase #7	$34.90	7.364%	$37.47	$37.47	$37.45	$37.50
7 purchase totals =	$404.75		$433.3970	$433.41	$433.35	$433.40