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	$198.63	11.549%	$221.5698	$221.57	$221.55	$221.60
Purchase #2	$225.88	10.696%	$250.0401	$250.04	$250.05	$250.00
Purchase #3	$142.50	10.568%	$157.5594	$157.56	$157.55	$157.60
Purchase #4	$227.77	11.656%	$254.3189	$254.32	$254.30	$254.30
Purchase #5	$51.39	6.126%	$54.5382	$54.54	$54.55	$54.50
Purchase #6	$28.56	8.348%	$30.9442	$30.94	$30.95	$30.90
Purchase #7	$83.72	10.528%	$92.534	$92.53	$92.55	$92.50
7 purchase totals =	$958.45		$1,061.5046	$1,061.50	$1,061.50	$1,061.40