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	$69.92	8.228%	$75.673	$75.67	$75.65	$75.70
Purchase #2	$172.50	11.694%	$192.6722	$192.67	$192.65	$192.70
Purchase #3	$20.71	7.558%	$22.2753	$22.28	$22.30	$22.30
Purchase #4	$55.71	6.314%	$59.2275	$59.23	$59.25	$59.20
Purchase #5	$191.59	4.874%	$200.9281	$200.93	$200.95	$200.90
Purchase #6	$69.51	13.543%	$78.9237	$78.92	$78.90	$78.90
Purchase #7	$185.95	11.711%	$207.7266	$207.73	$207.75	$207.70
7 purchase totals =	$765.89		$837.4264	$837.43	$837.45	$837.40