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	$197.55	10.568%	$218.4271	$218.43	$218.45	$218.40
Purchase #2	$59.33	3.680%	$61.5133	$61.51	$61.50	$61.50
Purchase #3	$27.66	13.796%	$31.476	$31.48	$31.50	$31.50
Purchase #4	$235.84	10.502%	$260.6079	$260.61	$260.60	$260.60
Purchase #5	$68.83	12.106%	$77.1626	$77.16	$77.15	$77.20
Purchase #6	$215.52	6.505%	$229.5396	$229.54	$229.55	$229.50
Purchase #7	$84.42	8.695%	$91.7603	$91.76	$91.75	$91.80
7 purchase totals =	$889.15		$970.4868	$970.49	$970.50	$970.50