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	$216.53	9.420%	$236.9271	$236.93	$236.95	$236.90
Purchase #2	$120.31	8.410%	$130.4281	$130.43	$130.45	$130.40
Purchase #3	$249.54	12.256%	$280.1236	$280.12	$280.10	$280.10
Purchase #4	$30.54	7.140%	$32.7206	$32.72	$32.70	$32.70
Purchase #5	$148.81	11.478%	$165.8904	$165.89	$165.90	$165.90
Purchase #6	$158.43	11.412%	$176.51	$176.51	$176.50	$176.50
Purchase #7	$136.46	8.664%	$148.2829	$148.28	$148.30	$148.30
7 purchase totals =	$1,060.62		$1,170.8827	$1,170.88	$1,170.90	$1,170.80