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	$40.29	11.717%	$45.0108	$45.01	$45.00	$45.00
Purchase #2	$21.78	3.599%	$22.5639	$22.56	$22.55	$22.60
Purchase #3	$229.50	11.506%	$255.9063	$255.91	$255.90	$255.90
Purchase #4	$39.34	4.129%	$40.9643	$40.96	$40.95	$41.00
Purchase #5	$167.89	3.450%	$173.6822	$173.68	$173.70	$173.70
Purchase #6	$86.66	4.279%	$90.3682	$90.37	$90.35	$90.40
Purchase #7	$131.78	5.709%	$139.3033	$139.30	$139.30	$139.30
7 purchase totals =	$717.24		$767.7990	$767.79	$767.75	$767.90