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	$227.45	13.192%	$257.4552	$257.46	$257.45	$257.50
Purchase #2	$62.90	11.112%	$69.8894	$69.89	$69.90	$69.90
Purchase #3	$13.76	3.345%	$14.2203	$14.22	$14.20	$14.20
Purchase #4	$6.97	7.197%	$7.4716	$7.47	$7.45	$7.50
Purchase #5	$89.76	11.397%	$99.9899	$99.99	$100.00	$100.00
Purchase #6	$80.80	12.723%	$91.0802	$91.08	$91.10	$91.10
Purchase #7	$209.54	11.621%	$233.8906	$233.89	$233.90	$233.90
7 purchase totals =	$691.18		$773.9972	$774.00	$774.00	$774.10