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	$193.44	5.748%	$204.5589	$204.56	$204.55	$204.60
Purchase #2	$101.53	4.474%	$106.0725	$106.07	$106.05	$106.10
Purchase #3	$6.64	12.312%	$7.4575	$7.46	$7.45	$7.50
Purchase #4	$57.30	6.742%	$61.1632	$61.16	$61.15	$61.20
Purchase #5	$167.89	10.347%	$185.2616	$185.26	$185.25	$185.30
Purchase #6	$247.55	6.827%	$264.4502	$264.45	$264.45	$264.50
Purchase #7	$65.83	10.376%	$72.6605	$72.66	$72.65	$72.70
7 purchase totals =	$840.18		$901.6244	$901.62	$901.55	$901.90