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	$221.44	8.588%	$240.4573	$240.46	$240.45	$240.50
Purchase #2	$197.25	10.306%	$217.5786	$217.58	$217.60	$217.60
Purchase #3	$133.30	8.762%	$144.9797	$144.98	$145.00	$145.00
Purchase #4	$177.77	12.156%	$199.3797	$199.38	$199.40	$199.40
Purchase #5	$35.33	6.655%	$37.6812	$37.68	$37.70	$37.70
Purchase #6	$161.88	7.679%	$174.3108	$174.31	$174.30	$174.30
Purchase #7	$223.82	11.872%	$250.3919	$250.39	$250.40	$250.40
7 purchase totals =	$1,150.79		$1,264.7792	$1,264.78	$1,264.85	$1,264.90