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	$211.85	13.767%	$241.0154	$241.02	$241.00	$241.00
Purchase #2	$133.45	9.721%	$146.4227	$146.42	$146.40	$146.40
Purchase #3	$142.82	9.832%	$156.8621	$156.86	$156.85	$156.90
Purchase #4	$136.84	10.660%	$151.4271	$151.43	$151.45	$151.40
Purchase #5	$243.28	8.531%	$264.0342	$264.03	$264.05	$264.00
Purchase #6	$154.95	11.434%	$172.667	$172.67	$172.65	$172.70
Purchase #7	$49.33	5.464%	$52.0254	$52.03	$52.05	$52.00
7 purchase totals =	$1,072.52		$1,184.4539	$1,184.46	$1,184.45	$1,184.40