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	$215.69	6.290%	$229.2569	$229.26	$229.25	$229.30
Purchase #2	$155.83	6.804%	$166.4327	$166.43	$166.45	$166.40
Purchase #3	$85.29	4.140%	$88.821	$88.82	$88.80	$88.80
Purchase #4	$48.31	5.322%	$50.8811	$50.88	$50.90	$50.90
Purchase #5	$101.52	4.678%	$106.2691	$106.27	$106.25	$106.30
Purchase #6	$38.86	10.747%	$43.0363	$43.04	$43.05	$43.00
Purchase #7	$91.59	4.256%	$95.4881	$95.49	$95.50	$95.50
7 purchase totals =	$737.09		$780.1852	$780.19	$780.20	$780.20