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	$142.59	9.119%	$155.5928	$155.59	$155.60	$155.60
Purchase #2	$85.46	12.173%	$95.863	$95.86	$95.85	$95.90
Purchase #3	$155.41	3.409%	$160.7079	$160.71	$160.70	$160.70
Purchase #4	$118.57	9.663%	$130.0274	$130.03	$130.05	$130.00
Purchase #5	$38.34	13.526%	$43.5259	$43.53	$43.55	$43.50
Purchase #6	$69.50	12.618%	$78.2695	$78.27	$78.25	$78.30
Purchase #7	$142.46	3.490%	$147.4319	$147.43	$147.45	$147.40
7 purchase totals =	$752.33		$811.4184	$811.42	$811.45	$811.40