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	$97.86	7.386%	$105.0879	$105.09	$105.10	$105.10
Purchase #2	$118.29	7.641%	$127.3285	$127.33	$127.35	$127.30
Purchase #3	$27.67	7.380%	$29.712	$29.71	$29.70	$29.70
Purchase #4	$59.79	4.869%	$62.7012	$62.70	$62.70	$62.70
Purchase #5	$165.89	10.605%	$183.4826	$183.48	$183.50	$183.50
Purchase #6	$158.43	10.157%	$174.5217	$174.52	$174.50	$174.50
Purchase #7	$158.44	6.758%	$169.1474	$169.15	$169.15	$169.10
7 purchase totals =	$786.37		$851.9813	$851.98	$852.00	$851.90