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	$198.47	11.784%	$221.8577	$221.86	$221.85	$221.90
Purchase #2	$245.83	11.284%	$273.5695	$273.57	$273.55	$273.60
Purchase #3	$180.90	6.726%	$193.0673	$193.07	$193.05	$193.10
Purchase #4	$175.51	8.498%	$190.4248	$190.42	$190.40	$190.40
Purchase #5	$54.68	7.144%	$58.5863	$58.59	$58.60	$58.60
Purchase #6	$120.50	9.150%	$131.5258	$131.53	$131.55	$131.50
Purchase #7	$32.59	3.486%	$33.7261	$33.73	$33.75	$33.70
7 purchase totals =	$1,008.48		$1,102.7575	$1,102.77	$1,102.75	$1,102.80