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	$114.62	7.644%	$123.3816	$123.38	$123.40	$123.40
Purchase #2	$57.25	11.674%	$63.9334	$63.93	$63.95	$63.90
Purchase #3	$123.75	3.241%	$127.7607	$127.76	$127.75	$127.80
Purchase #4	$99.36	5.863%	$105.1855	$105.19	$105.20	$105.20
Purchase #5	$95.68	10.457%	$105.6853	$105.69	$105.70	$105.70
Purchase #6	$169.84	7.572%	$182.7003	$182.70	$182.70	$182.70
Purchase #7	$62.62	7.829%	$67.5225	$67.52	$67.50	$67.50
7 purchase totals =	$723.12		$776.1693	$776.17	$776.20	$776.20