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	$95.39	6.782%	$101.8593	$101.86	$101.85	$101.90
Purchase #2	$10.87	11.511%	$12.1212	$12.12	$12.10	$12.10
Purchase #3	$141.56	4.350%	$147.7179	$147.72	$147.70	$147.70
Purchase #4	$87.37	12.378%	$98.1847	$98.18	$98.20	$98.20
Purchase #5	$128.83	4.654%	$134.8257	$134.83	$134.85	$134.80
Purchase #6	$68.69	5.628%	$72.5559	$72.56	$72.55	$72.60
Purchase #7	$54.31	9.646%	$59.5487	$59.55	$59.55	$59.50
7 purchase totals =	$587.02		$626.8134	$626.82	$626.80	$626.80