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	$215.62	5.109%	$226.636	$226.64	$226.65	$226.60
Purchase #2	$221.48	4.306%	$231.0169	$231.02	$231.00	$231.00
Purchase #3	$6.69	7.388%	$7.1843	$7.18	$7.20	$7.20
Purchase #4	$105.81	3.539%	$109.5546	$109.55	$109.55	$109.60
Purchase #5	$108.63	13.572%	$123.3733	$123.37	$123.35	$123.40
Purchase #6	$119.67	6.592%	$127.5586	$127.56	$127.55	$127.60
Purchase #7	$23.32	12.270%	$26.1814	$26.18	$26.20	$26.20
7 purchase totals =	$801.22		$851.5051	$851.50	$851.50	$851.60