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	$128.58	4.227%	$134.0151	$134.02	$134.00	$134.00
Purchase #2	$223.34	11.314%	$248.6087	$248.61	$248.60	$248.60
Purchase #3	$33.33	9.287%	$36.4254	$36.43	$36.45	$36.40
Purchase #4	$240.79	12.329%	$270.477	$270.48	$270.50	$270.50
Purchase #5	$158.64	13.186%	$179.5583	$179.56	$179.55	$179.60
Purchase #6	$130.78	3.446%	$135.2867	$135.29	$135.30	$135.30
Purchase #7	$78.87	4.660%	$82.5453	$82.55	$82.55	$82.50
7 purchase totals =	$994.33		$1,086.9165	$1,086.94	$1,086.95	$1,086.90