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	$188.89	4.149%	$196.727	$196.73	$196.75	$196.70
Purchase #2	$174.55	8.857%	$190.0099	$190.01	$190.00	$190.00
Purchase #3	$120.72	7.845%	$130.1905	$130.19	$130.20	$130.20
Purchase #4	$131.57	11.492%	$146.69	$146.69	$146.70	$146.70
Purchase #5	$148.64	13.741%	$169.0646	$169.06	$169.05	$169.10
Purchase #6	$180.63	4.212%	$188.2381	$188.24	$188.25	$188.20
Purchase #7	$209.56	6.217%	$222.5883	$222.59	$222.60	$222.60
7 purchase totals =	$1,154.56		$1,243.5084	$1,243.51	$1,243.55	$1,243.50