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	$189.73	12.237%	$212.9473	$212.95	$212.95	$212.90
Purchase #2	$12.28	9.782%	$13.4812	$13.48	$13.50	$13.50
Purchase #3	$83.64	5.565%	$88.2946	$88.29	$88.30	$88.30
Purchase #4	$249.76	6.315%	$265.5323	$265.53	$265.55	$265.50
Purchase #5	$21.42	4.713%	$22.4295	$22.43	$22.45	$22.40
Purchase #6	$59.77	11.239%	$66.4876	$66.49	$66.50	$66.50
Purchase #7	$141.45	10.460%	$156.2457	$156.25	$156.25	$156.20
7 purchase totals =	$758.05		$825.4182	$825.42	$825.50	$825.30