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	$7.26	11.157%	$8.07	$8.07	$8.05	$8.10
Purchase #2	$92.78	8.802%	$100.9465	$100.95	$100.95	$100.90
Purchase #3	$98.32	11.481%	$109.6081	$109.61	$109.60	$109.60
Purchase #4	$146.95	4.323%	$153.3026	$153.30	$153.30	$153.30
Purchase #5	$203.85	7.718%	$219.5831	$219.58	$219.60	$219.60
Purchase #6	$167.72	3.793%	$174.0816	$174.08	$174.10	$174.10
Purchase #7	$129.91	9.226%	$141.8955	$141.90	$141.90	$141.90
7 purchase totals =	$846.79		$907.4874	$907.49	$907.50	$907.50