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	$192.49	11.723%	$215.0556	$215.06	$215.05	$215.10
Purchase #2	$21.37	4.115%	$22.2494	$22.25	$22.25	$22.20
Purchase #3	$209.88	5.687%	$221.8159	$221.82	$221.80	$221.80
Purchase #4	$25.86	8.178%	$27.9748	$27.97	$27.95	$28.00
Purchase #5	$52.75	12.568%	$59.3796	$59.38	$59.40	$59.40
Purchase #6	$139.46	3.786%	$144.74	$144.74	$144.75	$144.70
Purchase #7	$214.78	4.116%	$223.6203	$223.62	$223.60	$223.60
7 purchase totals =	$856.59		$914.8356	$914.84	$914.80	$914.80