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	$105.68	3.661%	$109.5489	$109.55	$109.55	$109.50
Purchase #2	$234.51	13.194%	$265.4512	$265.45	$265.45	$265.50
Purchase #3	$245.28	8.801%	$266.8671	$266.87	$266.85	$266.90
Purchase #4	$38.44	7.789%	$41.4341	$41.43	$41.45	$41.40
Purchase #5	$17.46	10.132%	$19.229	$19.23	$19.25	$19.20
Purchase #6	$45.56	5.510%	$48.0704	$48.07	$48.05	$48.10
Purchase #7	$67.43	9.281%	$73.6882	$73.69	$73.70	$73.70
7 purchase totals =	$754.36		$824.2889	$824.29	$824.30	$824.30