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	$85.43	4.690%	$89.4367	$89.44	$89.45	$89.40
Purchase #2	$140.89	8.434%	$152.7727	$152.77	$152.75	$152.80
Purchase #3	$158.56	13.516%	$179.991	$179.99	$180.00	$180.00
Purchase #4	$138.86	5.782%	$146.8889	$146.89	$146.90	$146.90
Purchase #5	$60.65	6.709%	$64.719	$64.72	$64.70	$64.70
Purchase #6	$190.30	10.508%	$210.2967	$210.30	$210.30	$210.30
Purchase #7	$148.76	13.414%	$168.7147	$168.71	$168.70	$168.70
7 purchase totals =	$923.45		$1,012.8197	$1,012.82	$1,012.80	$1,012.80