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	$89.28	3.597%	$92.4914	$92.49	$92.50	$92.50
Purchase #2	$18.53	3.380%	$19.1563	$19.16	$19.15	$19.20
Purchase #3	$150.96	11.398%	$168.1664	$168.17	$168.15	$168.20
Purchase #4	$144.91	9.307%	$158.3968	$158.40	$158.40	$158.40
Purchase #5	$64.82	9.254%	$70.8184	$70.82	$70.80	$70.80
Purchase #6	$158.73	3.428%	$164.1713	$164.17	$164.15	$164.20
Purchase #7	$33.30	4.531%	$34.8088	$34.81	$34.80	$34.80
7 purchase totals =	$660.53		$708.0094	$708.02	$707.95	$708.10