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	$87.50	10.187%	$96.4136	$96.41	$96.40	$96.40
Purchase #2	$221.26	10.607%	$244.729	$244.73	$244.75	$244.70
Purchase #3	$90.57	10.726%	$100.2845	$100.28	$100.30	$100.30
Purchase #4	$83.43	7.711%	$89.8633	$89.86	$89.85	$89.90
Purchase #5	$33.59	8.458%	$36.431	$36.43	$36.45	$36.40
Purchase #6	$198.55	9.157%	$216.7312	$216.73	$216.75	$216.70
Purchase #7	$50.98	11.722%	$56.9559	$56.96	$56.95	$57.00
7 purchase totals =	$765.88		$841.4085	$841.40	$841.45	$841.40