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	$32.95	13.433%	$37.3762	$37.38	$37.40	$37.40
Purchase #2	$70.61	11.184%	$78.507	$78.51	$78.50	$78.50
Purchase #3	$58.34	6.853%	$62.338	$62.34	$62.35	$62.30
Purchase #4	$149.84	4.102%	$155.9864	$155.99	$156.00	$156.00
Purchase #5	$83.38	6.194%	$88.5446	$88.54	$88.55	$88.50
Purchase #6	$228.96	9.747%	$251.2767	$251.28	$251.30	$251.30
Purchase #7	$218.86	11.238%	$243.4555	$243.46	$243.45	$243.50
7 purchase totals =	$842.94		$917.4844	$917.50	$917.55	$917.50