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	$227.49	11.809%	$254.3543	$254.35	$254.35	$254.40
Purchase #2	$179.77	7.854%	$193.8891	$193.89	$193.90	$193.90
Purchase #3	$42.59	6.827%	$45.4976	$45.50	$45.50	$45.50
Purchase #4	$191.50	11.188%	$212.925	$212.93	$212.95	$212.90
Purchase #5	$40.55	3.401%	$41.9291	$41.93	$41.95	$41.90
Purchase #6	$35.38	8.522%	$38.3951	$38.40	$38.40	$38.40
Purchase #7	$85.30	10.334%	$94.1149	$94.11	$94.10	$94.10
7 purchase totals =	$802.58		$881.1051	$881.11	$881.15	$881.10