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	$247.81	10.638%	$274.172	$274.17	$274.15	$274.20
Purchase #2	$246.57	11.746%	$275.5321	$275.53	$275.55	$275.50
Purchase #3	$79.57	12.821%	$89.7717	$89.77	$89.75	$89.80
Purchase #4	$93.56	13.705%	$106.3824	$106.38	$106.40	$106.40
Purchase #5	$54.26	10.783%	$60.1109	$60.11	$60.10	$60.10
Purchase #6	$56.36	11.176%	$62.6588	$62.66	$62.65	$62.70
Purchase #7	$146.38	9.426%	$160.1778	$160.18	$160.20	$160.20
7 purchase totals =	$924.51		$1,028.8057	$1,028.80	$1,028.80	$1,028.90