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	$128.56	4.642%	$134.5278	$134.53	$134.55	$134.50
Purchase #2	$228.90	4.316%	$238.7793	$238.78	$238.80	$238.80
Purchase #3	$99.55	10.591%	$110.0933	$110.09	$110.10	$110.10
Purchase #4	$158.97	10.469%	$175.6126	$175.61	$175.60	$175.60
Purchase #5	$74.47	5.107%	$78.2732	$78.27	$78.25	$78.30
Purchase #6	$139.90	12.146%	$156.8923	$156.89	$156.90	$156.90
Purchase #7	$152.62	11.141%	$169.6234	$169.62	$169.60	$169.60
7 purchase totals =	$982.97		$1,063.8019	$1,063.79	$1,063.80	$1,063.80