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	$42.70	10.721%	$47.2779	$47.28	$47.30	$47.30
Purchase #2	$179.64	11.719%	$200.692	$200.69	$200.70	$200.70
Purchase #3	$176.69	11.243%	$196.5553	$196.56	$196.55	$196.60
Purchase #4	$220.81	5.695%	$233.3851	$233.39	$233.40	$233.40
Purchase #5	$191.54	7.702%	$206.2924	$206.29	$206.30	$206.30
Purchase #6	$75.46	11.753%	$84.3288	$84.33	$84.35	$84.30
Purchase #7	$10.99	5.632%	$11.609	$11.61	$11.60	$11.60
7 purchase totals =	$897.83		$980.1405	$980.15	$980.20	$980.20