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	$56.71	8.838%	$61.722	$61.72	$61.70	$61.70
Purchase #2	$126.57	12.423%	$142.2938	$142.29	$142.30	$142.30
Purchase #3	$157.51	9.574%	$172.59	$172.59	$172.60	$172.60
Purchase #4	$103.79	11.487%	$115.7124	$115.71	$115.70	$115.70
Purchase #5	$63.33	13.111%	$71.6332	$71.63	$71.65	$71.60
Purchase #6	$99.53	8.831%	$108.3195	$108.32	$108.30	$108.30
Purchase #7	$87.84	9.690%	$96.3517	$96.35	$96.35	$96.40
7 purchase totals =	$695.28		$768.6226	$768.61	$768.60	$768.60