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	$97.73	3.249%	$100.9052	$100.91	$100.90	$100.90
Purchase #2	$55.80	4.850%	$58.5063	$58.51	$58.50	$58.50
Purchase #3	$56.90	10.378%	$62.8051	$62.81	$62.80	$62.80
Purchase #4	$44.56	12.482%	$50.122	$50.12	$50.10	$50.10
Purchase #5	$116.41	9.480%	$127.4457	$127.45	$127.45	$127.40
Purchase #6	$190.33	4.237%	$198.3943	$198.39	$198.40	$198.40
Purchase #7	$182.65	10.194%	$201.2693	$201.27	$201.25	$201.30
7 purchase totals =	$744.38		$799.4479	$799.46	$799.40	$799.40