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	$66.89	9.162%	$73.0185	$73.02	$73.00	$73.00
Purchase #2	$206.77	10.449%	$228.3754	$228.38	$228.40	$228.40
Purchase #3	$67.47	6.727%	$72.0087	$72.01	$72.00	$72.00
Purchase #4	$6.50	9.116%	$7.0925	$7.09	$7.10	$7.10
Purchase #5	$82.29	11.352%	$91.6316	$91.63	$91.65	$91.60
Purchase #6	$158.78	6.862%	$169.6755	$169.68	$169.70	$169.70
Purchase #7	$136.45	4.515%	$142.6107	$142.61	$142.60	$142.60
7 purchase totals =	$725.15		$784.4129	$784.42	$784.45	$784.40