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	$196.72	13.838%	$223.9421	$223.94	$223.95	$223.90
Purchase #2	$117.28	8.541%	$127.2969	$127.30	$127.30	$127.30
Purchase #3	$199.51	11.308%	$222.0706	$222.07	$222.05	$222.10
Purchase #4	$41.39	3.308%	$42.7592	$42.76	$42.75	$42.80
Purchase #5	$86.71	5.498%	$91.4773	$91.48	$91.50	$91.50
Purchase #6	$61.73	11.624%	$68.9055	$68.91	$68.90	$68.90
Purchase #7	$233.73	10.452%	$258.1595	$258.16	$258.15	$258.20
7 purchase totals =	$937.07		$1,034.6111	$1,034.62	$1,034.60	$1,034.70