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	$92.71	12.209%	$104.029	$104.03	$104.05	$104.00
Purchase #2	$116.70	4.144%	$121.536	$121.54	$121.55	$121.50
Purchase #3	$223.72	6.432%	$238.1097	$238.11	$238.10	$238.10
Purchase #4	$82.66	4.833%	$86.655	$86.66	$86.65	$86.70
Purchase #5	$89.59	11.709%	$100.0801	$100.08	$100.10	$100.10
Purchase #6	$22.27	11.610%	$24.8555	$24.86	$24.85	$24.90
Purchase #7	$131.39	10.705%	$145.4553	$145.46	$145.45	$145.50
7 purchase totals =	$759.04		$820.7206	$820.74	$820.75	$820.80