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	$189.72	12.719%	$213.8505	$213.85	$213.85	$213.90
Purchase #2	$73.54	7.132%	$78.7849	$78.78	$78.80	$78.80
Purchase #3	$133.53	9.442%	$146.1379	$146.14	$146.15	$146.10
Purchase #4	$115.99	12.696%	$130.7161	$130.72	$130.70	$130.70
Purchase #5	$248.67	4.799%	$260.6037	$260.60	$260.60	$260.60
Purchase #6	$151.59	8.835%	$164.983	$164.98	$165.00	$165.00
Purchase #7	$92.81	8.413%	$100.6181	$100.62	$100.60	$100.60
7 purchase totals =	$1,005.85		$1,095.6942	$1,095.69	$1,095.70	$1,095.70