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	$69.58	12.599%	$78.3464	$78.35	$78.35	$78.30
Purchase #2	$242.41	12.874%	$273.6179	$273.62	$273.60	$273.60
Purchase #3	$84.25	13.782%	$95.8613	$95.86	$95.85	$95.90
Purchase #4	$188.97	8.811%	$205.6201	$205.62	$205.60	$205.60
Purchase #5	$106.31	9.219%	$116.1107	$116.11	$116.10	$116.10
Purchase #6	$153.64	4.664%	$160.8058	$160.81	$160.80	$160.80
Purchase #7	$142.66	9.165%	$155.7348	$155.73	$155.75	$155.70
7 purchase totals =	$987.82		$1,086.0970	$1,086.10	$1,086.05	$1,086.00