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	$179.83	11.558%	$200.6148	$200.61	$200.60	$200.60
Purchase #2	$238.50	7.200%	$255.672	$255.67	$255.65	$255.70
Purchase #3	$182.79	8.727%	$198.7421	$198.74	$198.75	$198.70
Purchase #4	$96.88	8.831%	$105.4355	$105.44	$105.45	$105.40
Purchase #5	$213.91	13.582%	$242.9633	$242.96	$242.95	$243.00
Purchase #6	$242.78	13.314%	$275.1037	$275.10	$275.10	$275.10
Purchase #7	$149.52	4.568%	$156.3501	$156.35	$156.35	$156.40
7 purchase totals =	$1,304.21		$1,434.8815	$1,434.87	$1,434.85	$1,434.90