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	$233.28	13.500%	$264.7728	$264.77	$264.75	$264.80
Purchase #2	$94.81	11.221%	$105.4486	$105.45	$105.45	$105.40
Purchase #3	$200.71	8.709%	$218.1898	$218.19	$218.20	$218.20
Purchase #4	$248.43	5.369%	$261.7682	$261.77	$261.75	$261.80
Purchase #5	$49.42	9.133%	$53.9335	$53.93	$53.95	$53.90
Purchase #6	$85.81	11.328%	$95.5306	$95.53	$95.55	$95.50
Purchase #7	$244.28	4.260%	$254.6863	$254.69	$254.70	$254.70
7 purchase totals =	$1,156.74		$1,254.3298	$1,254.33	$1,254.35	$1,254.30