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	$33.53	7.635%	$36.09	$36.09	$36.10	$36.10
Purchase #2	$92.67	13.819%	$105.4761	$105.48	$105.50	$105.50
Purchase #3	$127.66	4.658%	$133.6064	$133.61	$133.60	$133.60
Purchase #4	$46.52	3.143%	$47.9821	$47.98	$48.00	$48.00
Purchase #5	$182.90	9.863%	$200.9394	$200.94	$200.95	$200.90
Purchase #6	$168.32	7.140%	$180.338	$180.34	$180.35	$180.30
Purchase #7	$40.36	7.635%	$43.4415	$43.44	$43.45	$43.40
7 purchase totals =	$691.96		$747.8735	$747.88	$747.95	$747.80