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	$58.56	6.294%	$62.2458	$62.25	$62.25	$62.20
Purchase #2	$36.28	5.598%	$38.311	$38.31	$38.30	$38.30
Purchase #3	$236.97	5.246%	$249.4014	$249.40	$249.40	$249.40
Purchase #4	$70.73	8.132%	$76.4818	$76.48	$76.50	$76.50
Purchase #5	$37.43	12.599%	$42.1458	$42.15	$42.15	$42.10
Purchase #6	$86.96	4.362%	$90.7532	$90.75	$90.75	$90.80
Purchase #7	$141.94	7.334%	$152.3499	$152.35	$152.35	$152.30
7 purchase totals =	$668.87		$711.6889	$711.69	$711.70	$711.60