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	$43.59	4.245%	$45.4404	$45.44	$45.45	$45.40
Purchase #2	$78.96	8.243%	$85.4687	$85.47	$85.45	$85.50
Purchase #3	$205.33	9.802%	$225.4564	$225.46	$225.45	$225.50
Purchase #4	$202.60	10.271%	$223.409	$223.41	$223.40	$223.40
Purchase #5	$87.57	6.396%	$93.171	$93.17	$93.15	$93.20
Purchase #6	$109.72	12.621%	$123.5678	$123.57	$123.55	$123.60
Purchase #7	$41.66	7.777%	$44.8999	$44.90	$44.90	$44.90
7 purchase totals =	$769.43		$841.4132	$841.42	$841.35	$841.50