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	$168.55	11.645%	$188.1776	$188.18	$188.20	$188.20
Purchase #2	$178.29	4.551%	$186.404	$186.40	$186.40	$186.40
Purchase #3	$31.56	6.425%	$33.5877	$33.59	$33.60	$33.60
Purchase #4	$220.77	5.354%	$232.59	$232.59	$232.60	$232.60
Purchase #5	$223.25	10.412%	$246.4948	$246.49	$246.50	$246.50
Purchase #6	$65.84	6.781%	$70.3046	$70.30	$70.30	$70.30
Purchase #7	$57.96	5.679%	$61.2515	$61.25	$61.25	$61.30
7 purchase totals =	$946.22		$1,018.8102	$1,018.80	$1,018.85	$1,018.90