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	$191.31	9.787%	$210.0335	$210.03	$210.05	$210.00
Purchase #2	$241.58	9.246%	$263.9165	$263.92	$263.90	$263.90
Purchase #3	$66.44	4.845%	$69.659	$69.66	$69.65	$69.70
Purchase #4	$69.90	12.242%	$78.4572	$78.46	$78.45	$78.50
Purchase #5	$169.37	9.649%	$185.7125	$185.71	$185.70	$185.70
Purchase #6	$153.65	8.800%	$167.1712	$167.17	$167.15	$167.20
Purchase #7	$122.59	6.430%	$130.4725	$130.47	$130.45	$130.50
7 purchase totals =	$1,014.84		$1,105.4224	$1,105.42	$1,105.35	$1,105.50