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	$145.40	3.791%	$150.9121	$150.91	$150.90	$150.90
Purchase #2	$152.51	10.552%	$168.6029	$168.60	$168.60	$168.60
Purchase #3	$237.36	10.347%	$261.9196	$261.92	$261.90	$261.90
Purchase #4	$128.62	3.816%	$133.5281	$133.53	$133.55	$133.50
Purchase #5	$204.91	6.667%	$218.5713	$218.57	$218.55	$218.60
Purchase #6	$103.38	11.139%	$114.8955	$114.90	$114.90	$114.90
Purchase #7	$168.26	6.215%	$178.7174	$178.72	$178.70	$178.70
7 purchase totals =	$1,140.44		$1,227.1469	$1,227.15	$1,227.10	$1,227.10