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	$118.56	13.402%	$134.4494	$134.45	$134.45	$134.40
Purchase #2	$99.46	9.844%	$109.2508	$109.25	$109.25	$109.30
Purchase #3	$59.96	9.458%	$65.631	$65.63	$65.65	$65.60
Purchase #4	$134.35	3.873%	$139.5534	$139.55	$139.55	$139.60
Purchase #5	$228.72	10.800%	$253.4218	$253.42	$253.40	$253.40
Purchase #6	$32.82	6.763%	$35.0396	$35.04	$35.05	$35.00
Purchase #7	$52.70	8.149%	$56.9945	$56.99	$57.00	$57.00
7 purchase totals =	$726.57		$794.3405	$794.33	$794.35	$794.30