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	$164.75	10.565%	$182.1558	$182.16	$182.15	$182.20
Purchase #2	$107.95	11.607%	$120.4798	$120.48	$120.50	$120.50
Purchase #3	$125.97	13.426%	$142.8827	$142.88	$142.90	$142.90
Purchase #4	$90.56	10.612%	$100.1702	$100.17	$100.15	$100.20
Purchase #5	$91.75	12.242%	$102.982	$102.98	$103.00	$103.00
Purchase #6	$245.52	4.801%	$257.3074	$257.31	$257.30	$257.30
Purchase #7	$62.46	5.413%	$65.841	$65.84	$65.85	$65.80
7 purchase totals =	$888.96		$971.8189	$971.82	$971.85	$971.90