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	$148.90	11.454%	$165.955	$165.96	$165.95	$166.00
Purchase #2	$174.76	5.627%	$184.5937	$184.59	$184.60	$184.60
Purchase #3	$100.82	8.583%	$109.4734	$109.47	$109.45	$109.50
Purchase #4	$70.45	13.412%	$79.8988	$79.90	$79.90	$79.90
Purchase #5	$168.77	7.840%	$182.0016	$182.00	$182.00	$182.00
Purchase #6	$95.58	11.871%	$106.9263	$106.93	$106.95	$106.90
Purchase #7	$83.61	3.747%	$86.7429	$86.74	$86.75	$86.70
7 purchase totals =	$842.89		$915.5917	$915.59	$915.60	$915.60