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	$64.74	13.661%	$73.5841	$73.58	$73.60	$73.60
Purchase #2	$22.30	13.255%	$25.2559	$25.26	$25.25	$25.30
Purchase #3	$149.91	11.422%	$167.0327	$167.03	$167.05	$167.00
Purchase #4	$54.98	11.861%	$61.5012	$61.50	$61.50	$61.50
Purchase #5	$153.56	8.447%	$166.5312	$166.53	$166.55	$166.50
Purchase #6	$141.79	13.141%	$160.4226	$160.42	$160.40	$160.40
Purchase #7	$147.32	3.714%	$152.7915	$152.79	$152.80	$152.80
7 purchase totals =	$734.60		$807.1192	$807.11	$807.15	$807.10