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	$169.32	3.251%	$174.8246	$174.82	$174.80	$174.80
Purchase #2	$131.94	8.219%	$142.7841	$142.78	$142.80	$142.80
Purchase #3	$64.48	11.388%	$71.823	$71.82	$71.80	$71.80
Purchase #4	$222.99	6.642%	$237.801	$237.80	$237.80	$237.80
Purchase #5	$30.99	13.761%	$35.2545	$35.25	$35.25	$35.30
Purchase #6	$33.45	3.428%	$34.5967	$34.60	$34.60	$34.60
Purchase #7	$142.29	10.296%	$156.9402	$156.94	$156.95	$156.90
7 purchase totals =	$795.46		$854.0241	$854.01	$854.00	$854.00