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	$100.92	4.554%	$105.5159	$105.52	$105.50	$105.50
Purchase #2	$235.91	3.271%	$243.6266	$243.63	$243.65	$243.60
Purchase #3	$224.33	11.657%	$250.4801	$250.48	$250.50	$250.50
Purchase #4	$170.25	13.311%	$192.912	$192.91	$192.90	$192.90
Purchase #5	$63.31	9.640%	$69.4131	$69.41	$69.40	$69.40
Purchase #6	$161.71	7.283%	$173.4873	$173.49	$173.50	$173.50
Purchase #7	$101.28	5.228%	$106.5749	$106.57	$106.55	$106.60
7 purchase totals =	$1,057.71		$1,142.0099	$1,142.01	$1,142.00	$1,142.00