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	$127.75	11.748%	$142.7581	$142.76	$142.75	$142.80
Purchase #2	$203.44	13.722%	$231.356	$231.36	$231.35	$231.40
Purchase #3	$29.84	11.438%	$33.2531	$33.25	$33.25	$33.30
Purchase #4	$116.47	10.348%	$128.5223	$128.52	$128.50	$128.50
Purchase #5	$243.85	10.119%	$268.5252	$268.53	$268.55	$268.50
Purchase #6	$95.96	4.255%	$100.0431	$100.04	$100.05	$100.00
Purchase #7	$210.79	8.354%	$228.3994	$228.40	$228.40	$228.40
7 purchase totals =	$1,028.10		$1,132.8572	$1,132.86	$1,132.85	$1,132.90