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	$229.60	6.132%	$243.6791	$243.68	$243.70	$243.70
Purchase #2	$84.98	8.658%	$92.3376	$92.34	$92.35	$92.30
Purchase #3	$157.72	4.859%	$165.3836	$165.38	$165.40	$165.40
Purchase #4	$236.55	9.414%	$258.8188	$258.82	$258.80	$258.80
Purchase #5	$77.25	11.522%	$86.1507	$86.15	$86.15	$86.20
Purchase #6	$165.55	4.410%	$172.8508	$172.85	$172.85	$172.90
Purchase #7	$78.96	6.590%	$84.1635	$84.16	$84.15	$84.20
7 purchase totals =	$1,030.61		$1,103.3841	$1,103.38	$1,103.40	$1,103.50