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	$198.83	6.444%	$211.6426	$211.64	$211.65	$211.60
Purchase #2	$165.33	4.175%	$172.2325	$172.23	$172.25	$172.20
Purchase #3	$145.27	6.654%	$154.9363	$154.94	$154.95	$154.90
Purchase #4	$160.81	7.474%	$172.8289	$172.83	$172.85	$172.80
Purchase #5	$241.43	10.500%	$266.7802	$266.78	$266.80	$266.80
Purchase #6	$244.88	7.662%	$263.6427	$263.64	$263.65	$263.60
Purchase #7	$10.77	13.211%	$12.1928	$12.19	$12.20	$12.20
7 purchase totals =	$1,167.32		$1,254.2560	$1,254.25	$1,254.35	$1,254.10