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	$208.51	4.821%	$218.5623	$218.56	$218.55	$218.60
Purchase #2	$71.38	3.370%	$73.7855	$73.79	$73.80	$73.80
Purchase #3	$164.69	13.522%	$186.9594	$186.96	$186.95	$187.00
Purchase #4	$108.51	3.851%	$112.6887	$112.69	$112.70	$112.70
Purchase #5	$168.55	11.790%	$188.422	$188.42	$188.40	$188.40
Purchase #6	$7.59	4.346%	$7.9199	$7.92	$7.90	$7.90
Purchase #7	$97.92	11.805%	$109.4795	$109.48	$109.50	$109.50
7 purchase totals =	$827.15		$897.8173	$897.82	$897.80	$897.90