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	$185.56	13.359%	$210.349	$210.35	$210.35	$210.30
Purchase #2	$90.64	11.502%	$101.0654	$101.07	$101.05	$101.10
Purchase #3	$243.73	11.698%	$272.2415	$272.24	$272.25	$272.20
Purchase #4	$177.27	10.615%	$196.0872	$196.09	$196.10	$196.10
Purchase #5	$127.37	12.616%	$143.439	$143.44	$143.45	$143.40
Purchase #6	$183.78	12.526%	$206.8003	$206.80	$206.80	$206.80
Purchase #7	$49.27	13.313%	$55.8293	$55.83	$55.85	$55.80
7 purchase totals =	$1,057.62		$1,185.8117	$1,185.82	$1,185.85	$1,185.70