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	$43.35	12.415%	$48.7319	$48.73	$48.75	$48.70
Purchase #2	$40.61	4.622%	$42.487	$42.49	$42.50	$42.50
Purchase #3	$232.42	10.240%	$256.2198	$256.22	$256.20	$256.20
Purchase #4	$45.91	10.546%	$50.7517	$50.75	$50.75	$50.80
Purchase #5	$150.88	13.593%	$171.3891	$171.39	$171.40	$171.40
Purchase #6	$147.68	13.371%	$167.4263	$167.43	$167.45	$167.40
Purchase #7	$63.98	13.170%	$72.4062	$72.41	$72.40	$72.40
7 purchase totals =	$724.83		$809.4120	$809.42	$809.45	$809.40