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	$167.26	9.213%	$182.6697	$182.67	$182.65	$182.70
Purchase #2	$231.31	10.508%	$255.6161	$255.62	$255.60	$255.60
Purchase #3	$250.56	5.229%	$263.6618	$263.66	$263.65	$263.70
Purchase #4	$54.75	12.535%	$61.6129	$61.61	$61.60	$61.60
Purchase #5	$59.37	8.756%	$64.5684	$64.57	$64.55	$64.60
Purchase #6	$181.44	9.483%	$198.646	$198.65	$198.65	$198.60
Purchase #7	$110.43	11.580%	$123.2178	$123.22	$123.20	$123.20
7 purchase totals =	$1,055.12		$1,149.9927	$1,150.00	$1,149.90	$1,150.00