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	$171.90	11.443%	$191.5705	$191.57	$191.55	$191.60
Purchase #2	$70.94	10.630%	$78.4809	$78.48	$78.50	$78.50
Purchase #3	$150.45	6.465%	$160.1766	$160.18	$160.20	$160.20
Purchase #4	$87.74	4.294%	$91.5076	$91.51	$91.50	$91.50
Purchase #5	$85.67	13.212%	$96.9887	$96.99	$97.00	$97.00
Purchase #6	$131.39	10.794%	$145.5722	$145.57	$145.55	$145.60
Purchase #7	$67.44	3.745%	$69.9656	$69.97	$69.95	$70.00
7 purchase totals =	$765.53		$834.2621	$834.27	$834.25	$834.40