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	$161.61	13.206%	$182.9522	$182.95	$182.95	$183.00
Purchase #2	$74.52	8.590%	$80.9213	$80.92	$80.90	$80.90
Purchase #3	$74.66	4.793%	$78.2385	$78.24	$78.25	$78.20
Purchase #4	$28.39	10.172%	$31.2778	$31.28	$31.30	$31.30
Purchase #5	$192.46	9.221%	$210.2067	$210.21	$210.20	$210.20
Purchase #6	$162.32	3.769%	$168.4378	$168.44	$168.45	$168.40
Purchase #7	$88.56	7.495%	$95.1976	$95.20	$95.20	$95.20
7 purchase totals =	$782.52		$847.2319	$847.24	$847.25	$847.20