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	$97.87	8.354%	$106.0461	$106.05	$106.05	$106.00
Purchase #2	$31.99	7.766%	$34.4743	$34.47	$34.45	$34.50
Purchase #3	$189.76	5.713%	$200.601	$200.60	$200.60	$200.60
Purchase #4	$220.84	10.175%	$243.3105	$243.31	$243.30	$243.30
Purchase #5	$93.95	3.271%	$97.0231	$97.02	$97.00	$97.00
Purchase #6	$99.91	5.674%	$105.5789	$105.58	$105.60	$105.60
Purchase #7	$201.58	7.451%	$216.5997	$216.60	$216.60	$216.60
7 purchase totals =	$935.90		$1,003.6336	$1,003.63	$1,003.60	$1,003.60