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	$116.56	13.190%	$131.9343	$131.93	$131.95	$131.90
Purchase #2	$20.35	9.220%	$22.2263	$22.23	$22.25	$22.20
Purchase #3	$35.85	9.189%	$39.1443	$39.14	$39.15	$39.10
Purchase #4	$33.39	13.705%	$37.9661	$37.97	$37.95	$38.00
Purchase #5	$128.54	13.281%	$145.6114	$145.61	$145.60	$145.60
Purchase #6	$91.93	10.557%	$101.6351	$101.64	$101.65	$101.60
Purchase #7	$99.60	8.344%	$107.9106	$107.91	$107.90	$107.90
7 purchase totals =	$526.22		$586.4281	$586.43	$586.45	$586.30