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	$59.81	5.118%	$62.8711	$62.87	$62.85	$62.90
Purchase #2	$19.55	3.287%	$20.1926	$20.19	$20.20	$20.20
Purchase #3	$137.76	13.518%	$156.3824	$156.38	$156.40	$156.40
Purchase #4	$227.39	7.158%	$243.6666	$243.67	$243.65	$243.70
Purchase #5	$230.69	12.341%	$259.1595	$259.16	$259.15	$259.20
Purchase #6	$221.25	6.610%	$235.8746	$235.87	$235.85	$235.90
Purchase #7	$180.88	10.838%	$200.4838	$200.48	$200.50	$200.50
7 purchase totals =	$1,077.33		$1,178.6306	$1,178.62	$1,178.60	$1,178.80