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	$228.70	10.767%	$253.3241	$253.32	$253.30	$253.30
Purchase #2	$86.97	6.263%	$92.4169	$92.42	$92.40	$92.40
Purchase #3	$64.76	10.757%	$71.7262	$71.73	$71.75	$71.70
Purchase #4	$107.74	3.282%	$111.276	$111.28	$111.30	$111.30
Purchase #5	$130.94	7.865%	$141.2384	$141.24	$141.25	$141.20
Purchase #6	$25.93	8.111%	$28.0332	$28.03	$28.05	$28.00
Purchase #7	$116.43	12.381%	$130.8452	$130.85	$130.85	$130.80
7 purchase totals =	$761.47		$828.8600	$828.87	$828.90	$828.70