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	$63.46	9.172%	$69.2806	$69.28	$69.30	$69.30
Purchase #2	$84.26	6.493%	$89.731	$89.73	$89.75	$89.70
Purchase #3	$33.74	10.548%	$37.2989	$37.30	$37.30	$37.30
Purchase #4	$6.42	13.244%	$7.2703	$7.27	$7.25	$7.30
Purchase #5	$96.90	12.558%	$109.0687	$109.07	$109.05	$109.10
Purchase #6	$80.45	7.817%	$86.7388	$86.74	$86.75	$86.70
Purchase #7	$148.96	10.193%	$164.1435	$164.14	$164.15	$164.10
7 purchase totals =	$514.19		$563.5318	$563.53	$563.55	$563.50