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	$209.95	8.315%	$227.4073	$227.41	$227.40	$227.40
Purchase #2	$107.80	5.801%	$114.0535	$114.05	$114.05	$114.10
Purchase #3	$81.44	10.361%	$89.878	$89.88	$89.90	$89.90
Purchase #4	$85.91	10.198%	$94.6711	$94.67	$94.65	$94.70
Purchase #5	$145.27	7.431%	$156.065	$156.07	$156.05	$156.10
Purchase #6	$150.55	11.174%	$167.3725	$167.37	$167.35	$167.40
Purchase #7	$90.70	9.775%	$99.5659	$99.57	$99.55	$99.60
7 purchase totals =	$871.62		$949.0133	$949.02	$948.95	$949.20