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	$97.80	11.222%	$108.7751	$108.78	$108.80	$108.80
Purchase #2	$101.64	11.196%	$113.0196	$113.02	$113.00	$113.00
Purchase #3	$216.48	12.773%	$244.131	$244.13	$244.15	$244.10
Purchase #4	$77.54	11.627%	$86.5556	$86.56	$86.55	$86.60
Purchase #5	$106.31	7.462%	$114.2429	$114.24	$114.25	$114.20
Purchase #6	$152.74	7.791%	$164.64	$164.64	$164.65	$164.60
Purchase #7	$33.68	11.153%	$37.4363	$37.44	$37.45	$37.40
7 purchase totals =	$786.19		$868.8005	$868.81	$868.85	$868.70