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	$90.35	5.411%	$95.2388	$95.24	$95.25	$95.20
Purchase #2	$163.58	3.243%	$168.8849	$168.88	$168.90	$168.90
Purchase #3	$152.97	10.311%	$168.7427	$168.74	$168.75	$168.70
Purchase #4	$170.47	5.177%	$179.2952	$179.30	$179.30	$179.30
Purchase #5	$13.52	5.418%	$14.2525	$14.25	$14.25	$14.30
Purchase #6	$211.33	10.553%	$233.6317	$233.63	$233.65	$233.60
Purchase #7	$212.54	4.383%	$221.8556	$221.86	$221.85	$221.90
7 purchase totals =	$1,014.76		$1,081.9014	$1,081.90	$1,081.95	$1,081.90