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	$223.79	7.685%	$240.9883	$240.99	$241.00	$241.00
Purchase #2	$140.55	8.581%	$152.6106	$152.61	$152.60	$152.60
Purchase #3	$84.57	5.373%	$89.1139	$89.11	$89.10	$89.10
Purchase #4	$81.33	8.644%	$88.3602	$88.36	$88.35	$88.40
Purchase #5	$61.90	12.294%	$69.51	$69.51	$69.50	$69.50
Purchase #6	$54.86	10.123%	$60.4135	$60.41	$60.40	$60.40
Purchase #7	$45.35	3.261%	$46.8289	$46.83	$46.85	$46.80
7 purchase totals =	$692.35		$747.8254	$747.82	$747.80	$747.80