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	$185.44	8.353%	$200.9298	$200.93	$200.95	$200.90
Purchase #2	$172.52	9.673%	$189.2079	$189.21	$189.20	$189.20
Purchase #3	$31.32	12.414%	$35.2081	$35.21	$35.20	$35.20
Purchase #4	$36.38	11.697%	$40.6354	$40.64	$40.65	$40.60
Purchase #5	$192.52	4.158%	$200.525	$200.53	$200.55	$200.50
Purchase #6	$233.92	11.405%	$260.5986	$260.60	$260.60	$260.60
Purchase #7	$94.89	5.192%	$99.8167	$99.82	$99.80	$99.80
7 purchase totals =	$946.99		$1,026.9215	$1,026.94	$1,026.95	$1,026.80