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	$64.53	11.703%	$72.0819	$72.08	$72.10	$72.10
Purchase #2	$65.54	10.345%	$72.3201	$72.32	$72.30	$72.30
Purchase #3	$87.39	4.403%	$91.2378	$91.24	$91.25	$91.20
Purchase #4	$67.26	8.434%	$72.9327	$72.93	$72.95	$72.90
Purchase #5	$83.82	10.623%	$92.7242	$92.72	$92.70	$92.70
Purchase #6	$43.38	3.326%	$44.8228	$44.82	$44.80	$44.80
Purchase #7	$61.95	3.710%	$64.2483	$64.25	$64.25	$64.20
7 purchase totals =	$473.87		$510.3678	$510.36	$510.35	$510.20