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	$43.79	11.635%	$48.885	$48.89	$48.90	$48.90
Purchase #2	$227.26	9.243%	$248.2656	$248.27	$248.25	$248.30
Purchase #3	$86.56	12.748%	$97.5947	$97.59	$97.60	$97.60
Purchase #4	$173.85	8.272%	$188.2309	$188.23	$188.25	$188.20
Purchase #5	$211.95	5.669%	$223.9654	$223.97	$223.95	$224.00
Purchase #6	$140.50	8.262%	$152.1081	$152.11	$152.10	$152.10
Purchase #7	$136.55	11.483%	$152.23	$152.23	$152.25	$152.20
7 purchase totals =	$1,020.46		$1,111.2797	$1,111.29	$1,111.30	$1,111.30