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	$168.31	10.445%	$185.89	$185.89	$185.90	$185.90
Purchase #2	$246.30	11.224%	$273.9447	$273.94	$273.95	$273.90
Purchase #3	$146.74	7.490%	$157.7308	$157.73	$157.75	$157.70
Purchase #4	$7.54	10.234%	$8.3116	$8.31	$8.30	$8.30
Purchase #5	$31.55	10.856%	$34.9751	$34.98	$35.00	$35.00
Purchase #6	$139.34	13.332%	$157.9168	$157.92	$157.90	$157.90
Purchase #7	$239.27	6.693%	$255.2843	$255.28	$255.30	$255.30
7 purchase totals =	$979.05		$1,074.0533	$1,074.05	$1,074.10	$1,074.00