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	$204.71	5.818%	$216.62	$216.62	$216.60	$216.60
Purchase #2	$109.26	12.685%	$123.1196	$123.12	$123.10	$123.10
Purchase #3	$238.32	8.153%	$257.7502	$257.75	$257.75	$257.80
Purchase #4	$120.61	8.465%	$130.8196	$130.82	$130.80	$130.80
Purchase #5	$112.88	3.523%	$116.8568	$116.86	$116.85	$116.90
Purchase #6	$77.95	6.267%	$82.8351	$82.84	$82.85	$82.80
Purchase #7	$172.78	8.494%	$187.4559	$187.46	$187.45	$187.50
7 purchase totals =	$1,036.51		$1,115.4572	$1,115.47	$1,115.40	$1,115.50