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	$145.89	13.556%	$165.6668	$165.67	$165.65	$165.70
Purchase #2	$131.79	11.171%	$146.5123	$146.51	$146.50	$146.50
Purchase #3	$39.63	10.535%	$43.805	$43.81	$43.80	$43.80
Purchase #4	$103.91	4.486%	$108.5714	$108.57	$108.55	$108.60
Purchase #5	$188.38	12.277%	$211.5074	$211.51	$211.50	$211.50
Purchase #6	$184.50	7.741%	$198.7821	$198.78	$198.80	$198.80
Purchase #7	$33.32	13.324%	$37.7596	$37.76	$37.75	$37.80
7 purchase totals =	$827.42		$912.6046	$912.61	$912.55	$912.70