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	$222.35	10.211%	$245.0542	$245.05	$245.05	$245.10
Purchase #2	$17.40	5.336%	$18.3285	$18.33	$18.35	$18.30
Purchase #3	$83.48	13.773%	$94.9777	$94.98	$95.00	$95.00
Purchase #4	$227.50	4.832%	$238.4928	$238.49	$238.50	$238.50
Purchase #5	$134.53	11.560%	$150.0817	$150.08	$150.10	$150.10
Purchase #6	$25.31	10.119%	$27.8711	$27.87	$27.85	$27.90
Purchase #7	$187.89	11.212%	$208.9562	$208.96	$208.95	$209.00
7 purchase totals =	$898.46		$983.7622	$983.76	$983.80	$983.90