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	$116.38	3.632%	$120.6069	$120.61	$120.60	$120.60
Purchase #2	$9.92	4.711%	$10.3873	$10.39	$10.40	$10.40
Purchase #3	$79.44	5.234%	$83.5979	$83.60	$83.60	$83.60
Purchase #4	$139.28	12.649%	$156.8975	$156.90	$156.90	$156.90
Purchase #5	$139.78	7.384%	$150.1014	$150.10	$150.10	$150.10
Purchase #6	$50.88	3.866%	$52.847	$52.85	$52.85	$52.80
Purchase #7	$85.75	11.715%	$95.7956	$95.80	$95.80	$95.80
7 purchase totals =	$621.43		$670.2336	$670.25	$670.25	$670.20