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	$213.49	3.648%	$221.2781	$221.28	$221.30	$221.30
Purchase #2	$203.83	4.571%	$213.1471	$213.15	$213.15	$213.10
Purchase #3	$140.78	6.604%	$150.0771	$150.08	$150.10	$150.10
Purchase #4	$238.57	6.225%	$253.421	$253.42	$253.40	$253.40
Purchase #5	$54.71	12.226%	$61.3988	$61.40	$61.40	$61.40
Purchase #6	$56.85	13.749%	$64.6663	$64.67	$64.65	$64.70
Purchase #7	$51.61	3.372%	$53.3503	$53.35	$53.35	$53.40
7 purchase totals =	$959.84		$1,017.3387	$1,017.35	$1,017.35	$1,017.40