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	$26.62	11.111%	$29.5777	$29.58	$29.60	$29.60
Purchase #2	$199.38	10.215%	$219.7467	$219.75	$219.75	$219.70
Purchase #3	$244.31	5.767%	$258.3994	$258.40	$258.40	$258.40
Purchase #4	$106.66	12.428%	$119.9157	$119.92	$119.90	$119.90
Purchase #5	$53.55	10.690%	$59.2745	$59.27	$59.25	$59.30
Purchase #6	$211.90	4.873%	$222.2259	$222.23	$222.25	$222.20
Purchase #7	$101.88	12.602%	$114.7189	$114.72	$114.70	$114.70
7 purchase totals =	$944.30		$1,023.8588	$1,023.87	$1,023.85	$1,023.80