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	$228.86	4.162%	$238.3852	$238.39	$238.40	$238.40
Purchase #2	$211.39	12.771%	$238.3866	$238.39	$238.40	$238.40
Purchase #3	$249.62	6.661%	$266.2472	$266.25	$266.25	$266.20
Purchase #4	$155.27	9.335%	$169.7645	$169.76	$169.75	$169.80
Purchase #5	$84.90	11.722%	$94.852	$94.85	$94.85	$94.90
Purchase #6	$60.25	8.645%	$65.4586	$65.46	$65.45	$65.50
Purchase #7	$237.47	9.452%	$259.9157	$259.92	$259.90	$259.90
7 purchase totals =	$1,227.76		$1,333.0098	$1,333.02	$1,333.00	$1,333.10