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	$88.72	11.472%	$98.898	$98.90	$98.90	$98.90
Purchase #2	$99.44	4.619%	$104.0331	$104.03	$104.05	$104.00
Purchase #3	$163.89	9.309%	$179.1465	$179.15	$179.15	$179.10
Purchase #4	$173.58	5.175%	$182.5628	$182.56	$182.55	$182.60
Purchase #5	$113.53	6.147%	$120.5087	$120.51	$120.50	$120.50
Purchase #6	$155.25	4.727%	$162.5887	$162.59	$162.60	$162.60
Purchase #7	$105.46	9.802%	$115.7972	$115.80	$115.80	$115.80
7 purchase totals =	$899.87		$963.5350	$963.54	$963.55	$963.50