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	$187.62	11.688%	$209.549	$209.55	$209.55	$209.50
Purchase #2	$72.40	6.515%	$77.1169	$77.12	$77.10	$77.10
Purchase #3	$89.83	11.766%	$100.3994	$100.40	$100.40	$100.40
Purchase #4	$67.55	8.243%	$73.1181	$73.12	$73.10	$73.10
Purchase #5	$113.72	3.121%	$117.2692	$117.27	$117.25	$117.30
Purchase #6	$160.87	5.263%	$169.3366	$169.34	$169.35	$169.30
Purchase #7	$112.25	10.269%	$123.777	$123.78	$123.80	$123.80
7 purchase totals =	$804.24		$870.5662	$870.58	$870.55	$870.50