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	$174.96	9.282%	$191.1998	$191.20	$191.20	$191.20
Purchase #2	$167.51	6.836%	$178.961	$178.96	$178.95	$179.00
Purchase #3	$209.25	13.787%	$238.0993	$238.10	$238.10	$238.10
Purchase #4	$224.61	5.843%	$237.734	$237.73	$237.75	$237.70
Purchase #5	$203.93	4.784%	$213.686	$213.69	$213.70	$213.70
Purchase #6	$137.67	9.307%	$150.4829	$150.48	$150.50	$150.50
Purchase #7	$178.39	7.309%	$191.4285	$191.43	$191.45	$191.40
7 purchase totals =	$1,296.32		$1,401.5915	$1,401.59	$1,401.65	$1,401.60