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	$194.54	13.648%	$221.0908	$221.09	$221.10	$221.10
Purchase #2	$21.80	3.808%	$22.6301	$22.63	$22.65	$22.60
Purchase #3	$58.58	6.373%	$62.3133	$62.31	$62.30	$62.30
Purchase #4	$100.81	3.253%	$104.0893	$104.09	$104.10	$104.10
Purchase #5	$82.80	9.348%	$90.5401	$90.54	$90.55	$90.50
Purchase #6	$128.44	8.703%	$139.6181	$139.62	$139.60	$139.60
Purchase #7	$202.68	12.164%	$227.334	$227.33	$227.35	$227.30
7 purchase totals =	$789.65		$867.6157	$867.61	$867.65	$867.50