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	$94.91	7.866%	$102.3756	$102.38	$102.40	$102.40
Purchase #2	$146.75	7.103%	$157.1737	$157.17	$157.15	$157.20
Purchase #3	$165.75	9.745%	$181.9023	$181.90	$181.90	$181.90
Purchase #4	$123.46	6.783%	$131.8343	$131.83	$131.85	$131.80
Purchase #5	$205.76	7.718%	$221.6406	$221.64	$221.65	$221.60
Purchase #6	$179.60	10.729%	$198.8693	$198.87	$198.85	$198.90
Purchase #7	$22.49	10.297%	$24.8058	$24.81	$24.80	$24.80
7 purchase totals =	$938.72		$1,018.6016	$1,018.60	$1,018.60	$1,018.60