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	$217.83	7.616%	$234.4199	$234.42	$234.40	$234.40
Purchase #2	$53.28	11.184%	$59.2388	$59.24	$59.25	$59.20
Purchase #3	$163.44	11.220%	$181.778	$181.78	$181.80	$181.80
Purchase #4	$71.70	9.458%	$78.4814	$78.48	$78.50	$78.50
Purchase #5	$57.60	9.671%	$63.1705	$63.17	$63.15	$63.20
Purchase #6	$42.55	11.205%	$47.3177	$47.32	$47.30	$47.30
Purchase #7	$32.46	4.213%	$33.8275	$33.83	$33.85	$33.80
7 purchase totals =	$638.86		$698.2338	$698.24	$698.25	$698.20