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	$101.57	9.626%	$111.3471	$111.35	$111.35	$111.30
Purchase #2	$173.69	6.845%	$185.5791	$185.58	$185.60	$185.60
Purchase #3	$144.87	12.794%	$163.4047	$163.40	$163.40	$163.40
Purchase #4	$75.86	3.216%	$78.2997	$78.30	$78.30	$78.30
Purchase #5	$63.62	6.550%	$67.7871	$67.79	$67.80	$67.80
Purchase #6	$32.87	7.595%	$35.3665	$35.37	$35.35	$35.40
Purchase #7	$113.43	3.789%	$117.7279	$117.73	$117.75	$117.70
7 purchase totals =	$705.91		$759.5121	$759.52	$759.55	$759.50