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	$142.86	5.143%	$150.2073	$150.21	$150.20	$150.20
Purchase #2	$38.76	3.256%	$40.022	$40.02	$40.00	$40.00
Purchase #3	$224.32	4.223%	$233.793	$233.79	$233.80	$233.80
Purchase #4	$192.32	6.796%	$205.3901	$205.39	$205.40	$205.40
Purchase #5	$79.64	4.103%	$82.9076	$82.91	$82.90	$82.90
Purchase #6	$157.59	9.496%	$172.5547	$172.55	$172.55	$172.60
Purchase #7	$211.70	6.189%	$224.8021	$224.80	$224.80	$224.80
7 purchase totals =	$1,047.19		$1,109.6768	$1,109.67	$1,109.65	$1,109.70