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	$152.73	4.602%	$159.7586	$159.76	$159.75	$159.80
Purchase #2	$192.36	13.673%	$218.6614	$218.66	$218.65	$218.70
Purchase #3	$54.30	3.442%	$56.169	$56.17	$56.15	$56.20
Purchase #4	$137.94	13.775%	$156.9412	$156.94	$156.95	$156.90
Purchase #5	$182.60	7.401%	$196.1142	$196.11	$196.10	$196.10
Purchase #6	$149.86	12.596%	$168.7364	$168.74	$168.75	$168.70
Purchase #7	$18.66	11.808%	$20.8634	$20.86	$20.85	$20.90
7 purchase totals =	$888.45		$977.2442	$977.24	$977.20	$977.30