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	$200.85	8.182%	$217.2835	$217.28	$217.30	$217.30
Purchase #2	$186.54	6.441%	$198.555	$198.56	$198.55	$198.60
Purchase #3	$173.95	9.399%	$190.2996	$190.30	$190.30	$190.30
Purchase #4	$187.81	6.721%	$200.4327	$200.43	$200.45	$200.40
Purchase #5	$146.79	3.281%	$151.6062	$151.61	$151.60	$151.60
Purchase #6	$35.38	6.356%	$37.6288	$37.63	$37.65	$37.60
Purchase #7	$189.52	12.869%	$213.9093	$213.91	$213.90	$213.90
7 purchase totals =	$1,120.84		$1,209.7151	$1,209.72	$1,209.75	$1,209.70