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	$189.56	11.102%	$210.605	$210.61	$210.60	$210.60
Purchase #2	$59.55	3.376%	$61.5604	$61.56	$61.55	$61.60
Purchase #3	$150.90	11.796%	$168.7002	$168.70	$168.70	$168.70
Purchase #4	$197.98	5.742%	$209.348	$209.35	$209.35	$209.30
Purchase #5	$176.73	5.516%	$186.4784	$186.48	$186.50	$186.50
Purchase #6	$129.42	7.653%	$139.3245	$139.32	$139.30	$139.30
Purchase #7	$77.83	3.852%	$80.828	$80.83	$80.85	$80.80
7 purchase totals =	$981.97		$1,056.8445	$1,056.85	$1,056.85	$1,056.80