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	$67.76	7.206%	$72.6428	$72.64	$72.65	$72.60
Purchase #2	$22.72	8.567%	$24.6664	$24.67	$24.65	$24.70
Purchase #3	$92.35	6.659%	$98.4996	$98.50	$98.50	$98.50
Purchase #4	$243.47	6.738%	$259.875	$259.88	$259.90	$259.90
Purchase #5	$28.94	8.641%	$31.4407	$31.44	$31.45	$31.40
Purchase #6	$52.90	13.497%	$60.0399	$60.04	$60.05	$60.00
Purchase #7	$69.36	3.492%	$71.7821	$71.78	$71.80	$71.80
7 purchase totals =	$577.50		$618.9465	$618.95	$619.00	$618.90