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	$241.32	7.432%	$259.2549	$259.25	$259.25	$259.30
Purchase #2	$108.28	8.779%	$117.7859	$117.79	$117.80	$117.80
Purchase #3	$188.32	13.162%	$213.1067	$213.11	$213.10	$213.10
Purchase #4	$104.47	11.252%	$116.225	$116.23	$116.25	$116.20
Purchase #5	$84.89	5.570%	$89.6184	$89.62	$89.60	$89.60
Purchase #6	$30.43	5.868%	$32.2156	$32.22	$32.20	$32.20
Purchase #7	$138.59	4.271%	$144.5092	$144.51	$144.50	$144.50
7 purchase totals =	$896.30		$972.7157	$972.73	$972.70	$972.70