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	$195.88	9.842%	$215.1585	$215.16	$215.15	$215.20
Purchase #2	$51.96	6.686%	$55.434	$55.43	$55.45	$55.40
Purchase #3	$20.85	3.148%	$21.5064	$21.51	$21.50	$21.50
Purchase #4	$80.54	13.464%	$91.3839	$91.38	$91.40	$91.40
Purchase #5	$64.43	3.812%	$66.8861	$66.89	$66.90	$66.90
Purchase #6	$42.67	3.320%	$44.0866	$44.09	$44.10	$44.10
Purchase #7	$32.62	9.293%	$35.6514	$35.65	$35.65	$35.70
7 purchase totals =	$488.95		$530.1069	$530.11	$530.15	$530.20