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	$168.48	11.117%	$187.2099	$187.21	$187.20	$187.20
Purchase #2	$195.91	7.136%	$209.8901	$209.89	$209.90	$209.90
Purchase #3	$75.86	12.549%	$85.3797	$85.38	$85.40	$85.40
Purchase #4	$74.32	11.272%	$82.6974	$82.70	$82.70	$82.70
Purchase #5	$63.94	3.259%	$66.0238	$66.02	$66.00	$66.00
Purchase #6	$67.86	6.539%	$72.2974	$72.30	$72.30	$72.30
Purchase #7	$152.48	5.272%	$160.5187	$160.52	$160.50	$160.50
7 purchase totals =	$798.85		$864.0170	$864.02	$864.00	$864.00