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	$93.25	10.310%	$102.8641	$102.86	$102.85	$102.90
Purchase #2	$237.91	4.760%	$249.2345	$249.23	$249.25	$249.20
Purchase #3	$209.78	10.709%	$232.2453	$232.25	$232.25	$232.20
Purchase #4	$110.94	13.526%	$125.9457	$125.95	$125.95	$125.90
Purchase #5	$87.84	13.708%	$99.8811	$99.88	$99.90	$99.90
Purchase #6	$200.43	11.377%	$223.2329	$223.23	$223.25	$223.20
Purchase #7	$83.46	8.596%	$90.6342	$90.63	$90.65	$90.60
7 purchase totals =	$1,023.61		$1,124.0378	$1,124.03	$1,124.10	$1,123.90