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	$226.88	10.524%	$250.7569	$250.76	$250.75	$250.80
Purchase #2	$109.79	7.734%	$118.2812	$118.28	$118.30	$118.30
Purchase #3	$151.93	9.663%	$166.611	$166.61	$166.60	$166.60
Purchase #4	$107.27	3.579%	$111.1092	$111.11	$111.10	$111.10
Purchase #5	$137.93	3.651%	$142.9658	$142.97	$142.95	$143.00
Purchase #6	$203.59	8.284%	$220.4554	$220.46	$220.45	$220.50
Purchase #7	$122.67	5.357%	$129.2414	$129.24	$129.25	$129.20
7 purchase totals =	$1,060.06		$1,139.4209	$1,139.43	$1,139.40	$1,139.50