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	$37.40	11.559%	$41.7231	$41.72	$41.70	$41.70
Purchase #2	$142.73	5.219%	$150.1791	$150.18	$150.20	$150.20
Purchase #3	$136.80	11.512%	$152.5484	$152.55	$152.55	$152.50
Purchase #4	$216.77	4.523%	$226.5745	$226.57	$226.55	$226.60
Purchase #5	$42.91	5.150%	$45.1199	$45.12	$45.10	$45.10
Purchase #6	$126.39	5.488%	$133.3263	$133.33	$133.35	$133.30
Purchase #7	$86.46	7.640%	$93.0655	$93.07	$93.05	$93.10
7 purchase totals =	$789.46		$842.5368	$842.54	$842.50	$842.50