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	$212.64	3.413%	$219.8974	$219.90	$219.90	$219.90
Purchase #2	$144.50	6.766%	$154.2769	$154.28	$154.30	$154.30
Purchase #3	$152.47	11.178%	$169.5131	$169.51	$169.50	$169.50
Purchase #4	$179.55	5.437%	$189.3121	$189.31	$189.30	$189.30
Purchase #5	$78.56	5.386%	$82.7912	$82.79	$82.80	$82.80
Purchase #6	$49.65	10.432%	$54.8295	$54.83	$54.85	$54.80
Purchase #7	$7.95	4.372%	$8.2976	$8.30	$8.30	$8.30
7 purchase totals =	$825.32		$878.9178	$878.92	$878.95	$878.90