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	$184.72	4.813%	$193.6106	$193.61	$193.60	$193.60
Purchase #2	$147.28	5.652%	$155.6043	$155.60	$155.60	$155.60
Purchase #3	$166.56	11.244%	$185.288	$185.29	$185.30	$185.30
Purchase #4	$117.84	10.711%	$130.4618	$130.46	$130.45	$130.50
Purchase #5	$250.27	12.210%	$280.828	$280.83	$280.85	$280.80
Purchase #6	$33.74	6.367%	$35.8882	$35.89	$35.90	$35.90
Purchase #7	$193.48	13.335%	$219.2806	$219.28	$219.30	$219.30
7 purchase totals =	$1,093.89		$1,200.9615	$1,200.96	$1,201.00	$1,201.00