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	$140.45	9.163%	$153.3194	$153.32	$153.30	$153.30
Purchase #2	$220.38	5.866%	$233.3075	$233.31	$233.30	$233.30
Purchase #3	$128.77	3.256%	$132.9628	$132.96	$132.95	$133.00
Purchase #4	$163.33	3.499%	$169.0449	$169.04	$169.05	$169.00
Purchase #5	$123.47	3.288%	$127.5297	$127.53	$127.55	$127.50
Purchase #6	$170.85	11.475%	$190.455	$190.46	$190.45	$190.50
Purchase #7	$137.48	3.486%	$142.2726	$142.27	$142.25	$142.30
7 purchase totals =	$1,084.73		$1,148.8919	$1,148.89	$1,148.85	$1,148.90