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	$80.56	13.394%	$91.3502	$91.35	$91.35	$91.40
Purchase #2	$186.50	5.114%	$196.0376	$196.04	$196.05	$196.00
Purchase #3	$55.50	6.859%	$59.3067	$59.31	$59.30	$59.30
Purchase #4	$220.42	13.269%	$249.6675	$249.67	$249.65	$249.70
Purchase #5	$33.28	8.228%	$36.0183	$36.02	$36.00	$36.00
Purchase #6	$18.35	11.230%	$20.4107	$20.41	$20.40	$20.40
Purchase #7	$208.86	5.759%	$220.8882	$220.89	$220.90	$220.90
7 purchase totals =	$803.47		$873.6792	$873.69	$873.65	$873.70