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	$123.50	9.118%	$134.7607	$134.76	$134.75	$134.80
Purchase #2	$190.52	10.518%	$210.5589	$210.56	$210.55	$210.60
Purchase #3	$50.53	6.803%	$53.9676	$53.97	$53.95	$54.00
Purchase #4	$55.67	6.157%	$59.0976	$59.10	$59.10	$59.10
Purchase #5	$114.34	5.322%	$120.4252	$120.43	$120.45	$120.40
Purchase #6	$58.71	13.398%	$66.576	$66.58	$66.60	$66.60
Purchase #7	$28.57	10.734%	$31.6367	$31.64	$31.65	$31.60
7 purchase totals =	$621.84		$677.0227	$677.04	$677.05	$677.10