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	$32.80	9.539%	$35.9288	$35.93	$35.95	$35.90
Purchase #2	$80.35	3.254%	$82.9646	$82.96	$82.95	$83.00
Purchase #3	$71.59	3.179%	$73.8658	$73.87	$73.85	$73.90
Purchase #4	$122.79	6.296%	$130.5209	$130.52	$130.50	$130.50
Purchase #5	$229.97	3.681%	$238.4352	$238.44	$238.45	$238.40
Purchase #6	$94.97	10.389%	$104.8364	$104.84	$104.85	$104.80
Purchase #7	$181.80	4.701%	$190.3464	$190.35	$190.35	$190.30
7 purchase totals =	$814.27		$856.8981	$856.91	$856.90	$856.80