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	$93.89	12.227%	$105.3699	$105.37	$105.35	$105.40
Purchase #2	$133.66	5.672%	$141.2412	$141.24	$141.25	$141.20
Purchase #3	$142.32	4.143%	$148.2163	$148.22	$148.20	$148.20
Purchase #4	$171.44	6.773%	$183.0516	$183.05	$183.05	$183.10
Purchase #5	$123.88	7.666%	$133.3766	$133.38	$133.40	$133.40
Purchase #6	$145.68	7.550%	$156.6788	$156.68	$156.70	$156.70
Purchase #7	$156.86	5.440%	$165.3932	$165.39	$165.40	$165.40
7 purchase totals =	$967.73		$1,033.3276	$1,033.33	$1,033.35	$1,033.40