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	$152.45	13.404%	$172.8844	$172.88	$172.90	$172.90
Purchase #2	$116.78	12.567%	$131.4557	$131.46	$131.45	$131.50
Purchase #3	$98.58	13.805%	$112.189	$112.19	$112.20	$112.20
Purchase #4	$96.63	7.398%	$103.7787	$103.78	$103.80	$103.80
Purchase #5	$19.42	10.121%	$21.3855	$21.39	$21.40	$21.40
Purchase #6	$170.47	11.428%	$189.9513	$189.95	$189.95	$190.00
Purchase #7	$202.81	6.539%	$216.0717	$216.07	$216.05	$216.10
7 purchase totals =	$857.14		$947.7163	$947.72	$947.75	$947.90