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	$156.99	6.396%	$167.0311	$167.03	$167.05	$167.00
Purchase #2	$206.60	13.714%	$234.9331	$234.93	$234.95	$234.90
Purchase #3	$69.73	4.663%	$72.9815	$72.98	$73.00	$73.00
Purchase #4	$224.30	9.480%	$245.5636	$245.56	$245.55	$245.60
Purchase #5	$56.82	7.447%	$61.0514	$61.05	$61.05	$61.10
Purchase #6	$82.75	9.286%	$90.4342	$90.43	$90.45	$90.40
Purchase #7	$55.33	8.313%	$59.9296	$59.93	$59.95	$59.90
7 purchase totals =	$852.52		$931.9245	$931.91	$932.00	$931.90