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	$129.57	12.128%	$145.2842	$145.28	$145.30	$145.30
Purchase #2	$224.76	7.456%	$241.5181	$241.52	$241.50	$241.50
Purchase #3	$7.81	4.371%	$8.1514	$8.15	$8.15	$8.20
Purchase #4	$217.79	5.273%	$229.2741	$229.27	$229.25	$229.30
Purchase #5	$37.73	5.277%	$39.721	$39.72	$39.70	$39.70
Purchase #6	$239.43	4.806%	$250.937	$250.94	$250.95	$250.90
Purchase #7	$92.37	11.771%	$103.2429	$103.24	$103.25	$103.20
7 purchase totals =	$949.46		$1,018.1287	$1,018.12	$1,018.10	$1,018.10