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	$55.60	10.698%	$61.5481	$61.55	$61.55	$61.50
Purchase #2	$68.42	7.467%	$73.5289	$73.53	$73.55	$73.50
Purchase #3	$168.94	7.600%	$181.7794	$181.78	$181.80	$181.80
Purchase #4	$217.77	11.808%	$243.4843	$243.48	$243.50	$243.50
Purchase #5	$112.28	13.850%	$127.8308	$127.83	$127.85	$127.80
Purchase #6	$130.48	11.345%	$145.283	$145.28	$145.30	$145.30
Purchase #7	$108.66	7.390%	$116.69	$116.69	$116.70	$116.70
7 purchase totals =	$862.15		$950.1445	$950.14	$950.25	$950.10