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	$92.85	6.590%	$98.9688	$98.97	$98.95	$99.00
Purchase #2	$57.94	3.222%	$59.8068	$59.81	$59.80	$59.80
Purchase #3	$205.89	11.347%	$229.2523	$229.25	$229.25	$229.30
Purchase #4	$230.87	12.446%	$259.6041	$259.60	$259.60	$259.60
Purchase #5	$235.95	8.618%	$256.2842	$256.28	$256.30	$256.30
Purchase #6	$24.28	6.845%	$25.942	$25.94	$25.95	$25.90
Purchase #7	$22.39	11.242%	$24.9071	$24.91	$24.90	$24.90
7 purchase totals =	$870.17		$954.7653	$954.76	$954.75	$954.80