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	$142.98	13.354%	$162.0735	$162.07	$162.05	$162.10
Purchase #2	$125.29	4.192%	$130.5422	$130.54	$130.55	$130.50
Purchase #3	$85.40	12.238%	$95.8513	$95.85	$95.85	$95.90
Purchase #4	$159.32	5.227%	$167.6477	$167.65	$167.65	$167.60
Purchase #5	$227.74	7.709%	$245.2965	$245.30	$245.30	$245.30
Purchase #6	$90.35	9.144%	$98.6116	$98.61	$98.60	$98.60
Purchase #7	$121.56	10.366%	$134.1609	$134.16	$134.15	$134.20
7 purchase totals =	$952.64		$1,034.1837	$1,034.18	$1,034.15	$1,034.20