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	$168.41	8.533%	$182.7804	$182.78	$182.80	$182.80
Purchase #2	$98.92	4.722%	$103.591	$103.59	$103.60	$103.60
Purchase #3	$126.83	3.578%	$131.368	$131.37	$131.35	$131.40
Purchase #4	$16.46	12.465%	$18.5117	$18.51	$18.50	$18.50
Purchase #5	$8.90	5.313%	$9.3729	$9.37	$9.35	$9.40
Purchase #6	$154.65	3.761%	$160.4664	$160.47	$160.45	$160.50
Purchase #7	$142.31	12.614%	$160.261	$160.26	$160.25	$160.30
7 purchase totals =	$716.48		$766.3514	$766.35	$766.30	$766.50