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	$206.53	3.221%	$213.1823	$213.18	$213.20	$213.20
Purchase #2	$131.80	5.563%	$139.132	$139.13	$139.15	$139.10
Purchase #3	$219.77	9.834%	$241.3822	$241.38	$241.40	$241.40
Purchase #4	$96.57	13.442%	$109.5509	$109.55	$109.55	$109.60
Purchase #5	$199.28	5.302%	$209.8458	$209.85	$209.85	$209.80
Purchase #6	$75.44	3.570%	$78.1332	$78.13	$78.15	$78.10
Purchase #7	$89.51	4.352%	$93.4055	$93.41	$93.40	$93.40
7 purchase totals =	$1,018.90		$1,084.6319	$1,084.63	$1,084.70	$1,084.60