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	$94.38	5.277%	$99.3604	$99.36	$99.35	$99.40
Purchase #2	$153.94	12.444%	$173.0963	$173.10	$173.10	$173.10
Purchase #3	$211.56	6.872%	$226.0984	$226.10	$226.10	$226.10
Purchase #4	$135.43	12.310%	$152.1014	$152.10	$152.10	$152.10
Purchase #5	$230.83	10.318%	$254.647	$254.65	$254.65	$254.60
Purchase #6	$152.33	13.434%	$172.794	$172.79	$172.80	$172.80
Purchase #7	$87.65	9.418%	$95.9049	$95.90	$95.90	$95.90
7 purchase totals =	$1,066.12		$1,174.0024	$1,174.00	$1,174.00	$1,174.00