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	$90.99	11.590%	$101.5357	$101.54	$101.55	$101.50
Purchase #2	$151.43	6.139%	$160.7263	$160.73	$160.75	$160.70
Purchase #3	$150.70	7.801%	$162.4561	$162.46	$162.45	$162.50
Purchase #4	$94.26	6.112%	$100.0212	$100.02	$100.00	$100.00
Purchase #5	$206.85	10.539%	$228.6499	$228.65	$228.65	$228.60
Purchase #6	$72.77	6.194%	$77.2774	$77.28	$77.30	$77.30
Purchase #7	$190.72	11.855%	$213.3299	$213.33	$213.35	$213.30
7 purchase totals =	$957.72		$1,043.9965	$1,044.01	$1,044.05	$1,043.90