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	$73.58	6.705%	$78.5135	$78.51	$78.50	$78.50
Purchase #2	$88.25	7.415%	$94.7937	$94.79	$94.80	$94.80
Purchase #3	$162.35	6.373%	$172.6966	$172.70	$172.70	$172.70
Purchase #4	$152.27	12.304%	$171.0053	$171.01	$171.00	$171.00
Purchase #5	$154.61	10.705%	$171.161	$171.16	$171.15	$171.20
Purchase #6	$157.40	11.479%	$175.4679	$175.47	$175.45	$175.50
Purchase #7	$236.82	8.491%	$256.9284	$256.93	$256.95	$256.90
7 purchase totals =	$1,025.28		$1,120.5664	$1,120.57	$1,120.55	$1,120.60