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	$96.44	8.695%	$104.8255	$104.83	$104.85	$104.80
Purchase #2	$50.33	3.104%	$51.8922	$51.89	$51.90	$51.90
Purchase #3	$65.54	8.669%	$71.2217	$71.22	$71.20	$71.20
Purchase #4	$249.89	10.476%	$276.0685	$276.07	$276.05	$276.10
Purchase #5	$239.87	13.680%	$272.6842	$272.68	$272.70	$272.70
Purchase #6	$72.79	10.558%	$80.4752	$80.48	$80.50	$80.50
Purchase #7	$243.52	12.279%	$273.4218	$273.42	$273.40	$273.40
7 purchase totals =	$1,018.38		$1,130.5891	$1,130.59	$1,130.60	$1,130.60