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	$14.36	6.567%	$15.303	$15.30	$15.30	$15.30
Purchase #2	$178.81	3.676%	$185.3831	$185.38	$185.40	$185.40
Purchase #3	$142.56	10.329%	$157.285	$157.29	$157.30	$157.30
Purchase #4	$231.49	3.224%	$238.9532	$238.95	$238.95	$239.00
Purchase #5	$157.29	9.609%	$172.404	$172.40	$172.40	$172.40
Purchase #6	$234.93	7.810%	$253.278	$253.28	$253.30	$253.30
Purchase #7	$135.34	6.596%	$144.267	$144.27	$144.25	$144.30
7 purchase totals =	$1,094.78		$1,166.8733	$1,166.87	$1,166.90	$1,167.00