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	$130.82	7.656%	$140.8356	$140.84	$140.85	$140.80
Purchase #2	$55.77	6.155%	$59.2026	$59.20	$59.20	$59.20
Purchase #3	$84.73	12.122%	$95.001	$95.00	$95.00	$95.00
Purchase #4	$77.32	7.185%	$82.8754	$82.88	$82.90	$82.90
Purchase #5	$123.44	4.477%	$128.9664	$128.97	$128.95	$129.00
Purchase #6	$45.73	13.209%	$51.7705	$51.77	$51.75	$51.80
Purchase #7	$52.57	4.430%	$54.8989	$54.90	$54.90	$54.90
7 purchase totals =	$570.38		$613.5504	$613.56	$613.55	$613.60