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	$182.25	7.146%	$195.2736	$195.27	$195.25	$195.30
Purchase #2	$138.95	3.191%	$143.3839	$143.38	$143.40	$143.40
Purchase #3	$171.86	9.110%	$187.5164	$187.52	$187.50	$187.50
Purchase #4	$153.27	11.504%	$170.9022	$170.90	$170.90	$170.90
Purchase #5	$112.42	7.449%	$120.7942	$120.79	$120.80	$120.80
Purchase #6	$89.82	13.499%	$101.9448	$101.94	$101.95	$101.90
Purchase #7	$76.33	9.174%	$83.3325	$83.33	$83.35	$83.30
7 purchase totals =	$924.90		$1,003.1476	$1,003.13	$1,003.15	$1,003.10