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	$204.88	13.686%	$232.9199	$232.92	$232.90	$232.90
Purchase #2	$246.50	11.760%	$275.4884	$275.49	$275.50	$275.50
Purchase #3	$223.29	4.165%	$232.59	$232.59	$232.60	$232.60
Purchase #4	$150.56	4.385%	$157.1621	$157.16	$157.15	$157.20
Purchase #5	$36.51	3.245%	$37.6947	$37.69	$37.70	$37.70
Purchase #6	$40.61	5.822%	$42.9743	$42.97	$42.95	$43.00
Purchase #7	$85.89	12.686%	$96.786	$96.79	$96.80	$96.80
7 purchase totals =	$988.24		$1,075.6154	$1,075.61	$1,075.60	$1,075.70