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	$225.46	11.725%	$251.8952	$251.90	$251.90	$251.90
Purchase #2	$31.31	7.593%	$33.6874	$33.69	$33.70	$33.70
Purchase #3	$36.50	13.184%	$41.3122	$41.31	$41.30	$41.30
Purchase #4	$148.50	12.798%	$167.505	$167.51	$167.50	$167.50
Purchase #5	$141.91	6.611%	$151.2917	$151.29	$151.30	$151.30
Purchase #6	$65.94	11.160%	$73.2989	$73.30	$73.30	$73.30
Purchase #7	$243.91	8.534%	$264.7253	$264.73	$264.75	$264.70
7 purchase totals =	$893.53		$983.7157	$983.73	$983.75	$983.70