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	$247.60	7.615%	$266.4547	$266.45	$266.45	$266.50
Purchase #2	$84.52	5.566%	$89.2244	$89.22	$89.20	$89.20
Purchase #3	$179.60	9.123%	$195.9849	$195.98	$196.00	$196.00
Purchase #4	$44.71	7.489%	$48.0583	$48.06	$48.05	$48.10
Purchase #5	$71.56	3.106%	$73.7827	$73.78	$73.80	$73.80
Purchase #6	$152.48	11.245%	$169.6264	$169.63	$169.65	$169.60
Purchase #7	$28.70	9.607%	$31.4572	$31.46	$31.45	$31.50
7 purchase totals =	$809.17		$874.5886	$874.58	$874.60	$874.70