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	$101.87	3.674%	$105.6127	$105.61	$105.60	$105.60
Purchase #2	$30.39	7.445%	$32.6525	$32.65	$32.65	$32.70
Purchase #3	$24.66	4.758%	$25.8333	$25.83	$25.85	$25.80
Purchase #4	$13.94	4.313%	$14.5412	$14.54	$14.55	$14.50
Purchase #5	$56.60	13.519%	$64.2518	$64.25	$64.25	$64.30
Purchase #6	$145.46	3.284%	$150.2369	$150.24	$150.25	$150.20
Purchase #7	$160.30	13.221%	$181.4933	$181.49	$181.50	$181.50
7 purchase totals =	$533.22		$574.6217	$574.61	$574.65	$574.60