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	$32.51	4.364%	$33.9287	$33.93	$33.95	$33.90
Purchase #2	$226.41	10.462%	$250.097	$250.10	$250.10	$250.10
Purchase #3	$144.30	8.330%	$156.3202	$156.32	$156.30	$156.30
Purchase #4	$123.43	10.590%	$136.5012	$136.50	$136.50	$136.50
Purchase #5	$198.33	10.504%	$219.1626	$219.16	$219.15	$219.20
Purchase #6	$217.87	12.590%	$245.2998	$245.30	$245.30	$245.30
Purchase #7	$198.74	11.854%	$222.2986	$222.30	$222.30	$222.30
7 purchase totals =	$1,141.59		$1,263.6081	$1,263.61	$1,263.60	$1,263.60