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	$102.37	8.675%	$111.2506	$111.25	$111.25	$111.30
Purchase #2	$37.53	10.421%	$41.441	$41.44	$41.45	$41.40
Purchase #3	$33.89	10.102%	$37.3136	$37.31	$37.30	$37.30
Purchase #4	$67.89	13.597%	$77.121	$77.12	$77.10	$77.10
Purchase #5	$178.30	10.120%	$196.344	$196.34	$196.35	$196.30
Purchase #6	$133.59	5.528%	$140.9749	$140.97	$140.95	$141.00
Purchase #7	$216.45	12.318%	$243.1123	$243.11	$243.10	$243.10
7 purchase totals =	$770.02		$847.5574	$847.54	$847.50	$847.50