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	$148.56	13.336%	$168.372	$168.37	$168.35	$168.40
Purchase #2	$164.74	13.582%	$187.115	$187.12	$187.10	$187.10
Purchase #3	$78.42	8.828%	$85.3429	$85.34	$85.35	$85.30
Purchase #4	$215.38	10.811%	$238.6647	$238.66	$238.65	$238.70
Purchase #5	$54.88	3.279%	$56.6795	$56.68	$56.70	$56.70
Purchase #6	$30.44	8.227%	$32.9443	$32.94	$32.95	$32.90
Purchase #7	$194.41	7.772%	$209.5195	$209.52	$209.50	$209.50
7 purchase totals =	$886.83		$978.6379	$978.63	$978.60	$978.60