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	$63.71	13.740%	$72.4638	$72.46	$72.45	$72.50
Purchase #2	$92.53	8.517%	$100.4108	$100.41	$100.40	$100.40
Purchase #3	$83.47	11.373%	$92.963	$92.96	$92.95	$93.00
Purchase #4	$88.90	13.368%	$100.7842	$100.78	$100.80	$100.80
Purchase #5	$30.69	8.597%	$33.3284	$33.33	$33.35	$33.30
Purchase #6	$220.66	11.755%	$246.5986	$246.60	$246.60	$246.60
Purchase #7	$113.52	8.796%	$123.5052	$123.51	$123.50	$123.50
7 purchase totals =	$693.48		$770.0540	$770.05	$770.05	$770.10