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	$199.49	5.621%	$210.7033	$210.70	$210.70	$210.70
Purchase #2	$17.54	4.660%	$18.3574	$18.36	$18.35	$18.40
Purchase #3	$135.83	5.211%	$142.9081	$142.91	$142.90	$142.90
Purchase #4	$25.36	10.642%	$28.0588	$28.06	$28.05	$28.10
Purchase #5	$173.49	9.420%	$189.8328	$189.83	$189.85	$189.80
Purchase #6	$98.42	5.524%	$103.8567	$103.86	$103.85	$103.90
Purchase #7	$59.38	4.188%	$61.8668	$61.87	$61.85	$61.90
7 purchase totals =	$709.51		$755.5839	$755.59	$755.55	$755.70