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	$74.94	3.369%	$77.4647	$77.46	$77.45	$77.50
Purchase #2	$151.35	5.296%	$159.3655	$159.37	$159.35	$159.40
Purchase #3	$61.97	6.345%	$65.902	$65.90	$65.90	$65.90
Purchase #4	$155.56	8.274%	$168.431	$168.43	$168.45	$168.40
Purchase #5	$92.25	3.533%	$95.5092	$95.51	$95.50	$95.50
Purchase #6	$79.84	11.503%	$89.024	$89.02	$89.00	$89.00
Purchase #7	$173.61	4.444%	$181.3252	$181.33	$181.35	$181.30
7 purchase totals =	$789.52		$837.0216	$837.02	$837.00	$837.00