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	$103.58	8.166%	$112.0383	$112.04	$112.05	$112.00
Purchase #2	$67.40	13.245%	$76.3271	$76.33	$76.35	$76.30
Purchase #3	$26.50	3.600%	$27.454	$27.45	$27.45	$27.50
Purchase #4	$38.42	10.573%	$42.4821	$42.48	$42.50	$42.50
Purchase #5	$71.28	8.510%	$77.3459	$77.35	$77.35	$77.30
Purchase #6	$242.73	8.665%	$263.7626	$263.76	$263.75	$263.80
Purchase #7	$205.37	4.629%	$214.8766	$214.88	$214.90	$214.90
7 purchase totals =	$755.28		$814.2866	$814.29	$814.35	$814.30