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	$41.84	4.560%	$43.7479	$43.75	$43.75	$43.70
Purchase #2	$84.87	4.745%	$88.8971	$88.90	$88.90	$88.90
Purchase #3	$37.61	12.801%	$42.4245	$42.42	$42.40	$42.40
Purchase #4	$170.26	3.494%	$176.2089	$176.21	$176.20	$176.20
Purchase #5	$24.78	13.451%	$28.1132	$28.11	$28.10	$28.10
Purchase #6	$156.57	10.427%	$172.8956	$172.90	$172.90	$172.90
Purchase #7	$10.34	7.738%	$11.1401	$11.14	$11.15	$11.10
7 purchase totals =	$526.27		$563.4273	$563.43	$563.40	$563.30