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	$67.64	6.357%	$71.9399	$71.94	$71.95	$71.90
Purchase #2	$209.89	10.509%	$231.9473	$231.95	$231.95	$231.90
Purchase #3	$12.78	11.407%	$14.2378	$14.24	$14.25	$14.20
Purchase #4	$60.91	4.459%	$63.626	$63.63	$63.65	$63.60
Purchase #5	$98.99	12.809%	$111.6696	$111.67	$111.65	$111.70
Purchase #6	$199.89	6.369%	$212.621	$212.62	$212.60	$212.60
Purchase #7	$225.59	4.278%	$235.2407	$235.24	$235.25	$235.20
7 purchase totals =	$875.69		$941.2823	$941.29	$941.30	$941.10