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	$146.88	13.809%	$167.1627	$167.16	$167.15	$167.20
Purchase #2	$179.30	11.731%	$200.3337	$200.33	$200.35	$200.30
Purchase #3	$126.45	4.151%	$131.6989	$131.70	$131.70	$131.70
Purchase #4	$72.35	6.703%	$77.1996	$77.20	$77.20	$77.20
Purchase #5	$166.46	8.143%	$180.0148	$180.01	$180.00	$180.00
Purchase #6	$165.32	8.766%	$179.812	$179.81	$179.80	$179.80
Purchase #7	$126.96	7.660%	$136.6851	$136.69	$136.70	$136.70
7 purchase totals =	$983.72		$1,072.9068	$1,072.90	$1,072.90	$1,072.90