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	$130.73	11.869%	$146.2463	$146.25	$146.25	$146.20
Purchase #2	$66.54	7.251%	$71.3648	$71.36	$71.35	$71.40
Purchase #3	$183.86	12.184%	$206.2615	$206.26	$206.25	$206.30
Purchase #4	$241.26	12.286%	$270.9012	$270.90	$270.90	$270.90
Purchase #5	$218.88	12.564%	$246.3801	$246.38	$246.40	$246.40
Purchase #6	$104.46	6.313%	$111.0546	$111.05	$111.05	$111.10
Purchase #7	$12.70	6.185%	$13.4855	$13.49	$13.50	$13.50
7 purchase totals =	$958.43		$1,065.6940	$1,065.69	$1,065.70	$1,065.80