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	$59.61	9.188%	$65.087	$65.09	$65.10	$65.10
Purchase #2	$147.83	6.730%	$157.779	$157.78	$157.80	$157.80
Purchase #3	$204.58	8.665%	$222.3069	$222.31	$222.30	$222.30
Purchase #4	$90.93	8.773%	$98.9073	$98.91	$98.90	$98.90
Purchase #5	$131.71	6.481%	$140.2461	$140.25	$140.25	$140.20
Purchase #6	$127.98	11.670%	$142.9153	$142.92	$142.90	$142.90
Purchase #7	$168.95	13.580%	$191.8934	$191.89	$191.90	$191.90
7 purchase totals =	$931.59		$1,019.1350	$1,019.15	$1,019.15	$1,019.10