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	$244.31	7.730%	$263.1952	$263.20	$263.20	$263.20
Purchase #2	$68.63	6.710%	$73.2351	$73.24	$73.25	$73.20
Purchase #3	$227.72	11.333%	$253.5275	$253.53	$253.55	$253.50
Purchase #4	$101.86	10.418%	$112.4718	$112.47	$112.45	$112.50
Purchase #5	$82.47	10.159%	$90.8481	$90.85	$90.85	$90.80
Purchase #6	$163.41	3.841%	$169.6866	$169.69	$169.70	$169.70
Purchase #7	$95.82	7.548%	$103.0525	$103.05	$103.05	$103.10
7 purchase totals =	$984.22		$1,066.0168	$1,066.03	$1,066.05	$1,066.00