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	$127.95	10.440%	$141.308	$141.31	$141.30	$141.30
Purchase #2	$194.75	9.327%	$212.9143	$212.91	$212.90	$212.90
Purchase #3	$43.52	13.392%	$49.3482	$49.35	$49.35	$49.30
Purchase #4	$240.42	5.284%	$253.1238	$253.12	$253.10	$253.10
Purchase #5	$65.39	11.543%	$72.938	$72.94	$72.95	$72.90
Purchase #6	$100.93	11.677%	$112.7156	$112.72	$112.70	$112.70
Purchase #7	$66.92	7.282%	$71.7931	$71.79	$71.80	$71.80
7 purchase totals =	$839.88		$914.1410	$914.14	$914.10	$914.00