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	$219.69	3.604%	$227.6076	$227.61	$227.60	$227.60
Purchase #2	$246.69	13.564%	$280.151	$280.15	$280.15	$280.20
Purchase #3	$115.47	10.731%	$127.8611	$127.86	$127.85	$127.90
Purchase #4	$94.74	5.437%	$99.891	$99.89	$99.90	$99.90
Purchase #5	$229.94	10.334%	$253.702	$253.70	$253.70	$253.70
Purchase #6	$160.29	12.376%	$180.1275	$180.13	$180.15	$180.10
Purchase #7	$29.32	12.801%	$33.0733	$33.07	$33.05	$33.10
7 purchase totals =	$1,096.14		$1,202.4135	$1,202.41	$1,202.40	$1,202.50