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	$129.71	8.691%	$140.9831	$140.98	$141.00	$141.00
Purchase #2	$150.90	9.302%	$164.9367	$164.94	$164.95	$164.90
Purchase #3	$54.94	8.772%	$59.7593	$59.76	$59.75	$59.80
Purchase #4	$19.63	4.294%	$20.4729	$20.47	$20.45	$20.50
Purchase #5	$93.48	13.217%	$105.8353	$105.84	$105.85	$105.80
Purchase #6	$71.55	7.385%	$76.834	$76.83	$76.85	$76.80
Purchase #7	$191.73	3.353%	$198.1587	$198.16	$198.15	$198.20
7 purchase totals =	$711.94		$766.9800	$766.98	$767.00	$767.00