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	$185.49	6.129%	$196.8587	$196.86	$196.85	$196.90
Purchase #2	$139.93	4.852%	$146.7194	$146.72	$146.70	$146.70
Purchase #3	$240.97	5.640%	$254.5607	$254.56	$254.55	$254.60
Purchase #4	$145.69	3.328%	$150.5386	$150.54	$150.55	$150.50
Purchase #5	$89.56	12.608%	$100.8517	$100.85	$100.85	$100.90
Purchase #6	$121.60	12.703%	$137.0468	$137.05	$137.05	$137.00
Purchase #7	$23.26	8.788%	$25.3041	$25.30	$25.30	$25.30
7 purchase totals =	$946.50		$1,011.8800	$1,011.88	$1,011.85	$1,011.90