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	$107.80	4.571%	$112.7275	$112.73	$112.75	$112.70
Purchase #2	$98.61	5.240%	$103.7772	$103.78	$103.80	$103.80
Purchase #3	$85.39	7.234%	$91.5671	$91.57	$91.55	$91.60
Purchase #4	$151.37	11.872%	$169.3406	$169.34	$169.35	$169.30
Purchase #5	$222.36	8.862%	$242.0655	$242.07	$242.05	$242.10
Purchase #6	$96.64	7.359%	$103.7517	$103.75	$103.75	$103.80
Purchase #7	$200.50	12.855%	$226.2743	$226.27	$226.25	$226.30
7 purchase totals =	$962.67		$1,049.5039	$1,049.51	$1,049.50	$1,049.60