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	$188.95	12.152%	$211.9112	$211.91	$211.90	$211.90
Purchase #2	$155.36	4.688%	$162.6433	$162.64	$162.65	$162.60
Purchase #3	$59.76	12.518%	$67.2408	$67.24	$67.25	$67.20
Purchase #4	$173.38	5.491%	$182.9003	$182.90	$182.90	$182.90
Purchase #5	$14.46	8.863%	$15.7416	$15.74	$15.75	$15.70
Purchase #6	$234.56	4.643%	$245.4506	$245.45	$245.45	$245.50
Purchase #7	$190.57	12.215%	$213.8481	$213.85	$213.85	$213.80
7 purchase totals =	$1,017.04		$1,099.7359	$1,099.73	$1,099.75	$1,099.60