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	$32.75	3.627%	$33.9378	$33.94	$33.95	$33.90
Purchase #2	$237.93	8.752%	$258.7536	$258.75	$258.75	$258.80
Purchase #3	$101.79	7.150%	$109.068	$109.07	$109.05	$109.10
Purchase #4	$245.93	13.723%	$279.679	$279.68	$279.70	$279.70
Purchase #5	$31.36	6.530%	$33.4078	$33.41	$33.40	$33.40
Purchase #6	$97.89	10.194%	$107.8689	$107.87	$107.85	$107.90
Purchase #7	$64.76	11.399%	$72.142	$72.14	$72.15	$72.10
7 purchase totals =	$812.41		$894.8571	$894.86	$894.85	$894.90