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	$66.63	11.442%	$74.2538	$74.25	$74.25	$74.30
Purchase #2	$219.54	8.736%	$238.719	$238.72	$238.70	$238.70
Purchase #3	$78.89	7.461%	$84.776	$84.78	$84.80	$84.80
Purchase #4	$32.54	10.668%	$36.0114	$36.01	$36.00	$36.00
Purchase #5	$214.47	4.387%	$223.8788	$223.88	$223.90	$223.90
Purchase #6	$122.93	12.142%	$137.8562	$137.86	$137.85	$137.90
Purchase #7	$102.33	6.574%	$109.0572	$109.06	$109.05	$109.10
7 purchase totals =	$837.33		$904.5524	$904.56	$904.55	$904.70