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	$196.33	13.309%	$222.4596	$222.46	$222.45	$222.50
Purchase #2	$8.59	6.269%	$9.1285	$9.13	$9.15	$9.10
Purchase #3	$196.99	3.409%	$203.7054	$203.71	$203.70	$203.70
Purchase #4	$136.51	4.501%	$142.6543	$142.65	$142.65	$142.70
Purchase #5	$81.53	10.720%	$90.27	$90.27	$90.25	$90.30
Purchase #6	$128.30	10.828%	$142.1923	$142.19	$142.20	$142.20
Purchase #7	$17.78	5.837%	$18.8178	$18.82	$18.80	$18.80
7 purchase totals =	$766.03		$829.2279	$829.23	$829.20	$829.30