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	$172.53	10.134%	$190.0142	$190.01	$190.00	$190.00
Purchase #2	$45.74	10.685%	$50.6273	$50.63	$50.65	$50.60
Purchase #3	$35.88	12.766%	$40.4604	$40.46	$40.45	$40.50
Purchase #4	$234.67	12.652%	$264.3604	$264.36	$264.35	$264.40
Purchase #5	$85.75	4.683%	$89.7657	$89.77	$89.75	$89.80
Purchase #6	$239.33	5.643%	$252.8354	$252.84	$252.85	$252.80
Purchase #7	$101.25	13.443%	$114.861	$114.86	$114.85	$114.90
7 purchase totals =	$915.15		$1,002.9244	$1,002.93	$1,002.90	$1,003.00