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	$95.67	6.336%	$101.7317	$101.73	$101.75	$101.70
Purchase #2	$218.89	6.518%	$233.1573	$233.16	$233.15	$233.20
Purchase #3	$53.72	10.400%	$59.3069	$59.31	$59.30	$59.30
Purchase #4	$96.42	5.682%	$101.8986	$101.90	$101.90	$101.90
Purchase #5	$68.87	5.222%	$72.4664	$72.47	$72.45	$72.50
Purchase #6	$246.60	5.177%	$259.3665	$259.37	$259.35	$259.40
Purchase #7	$31.40	5.418%	$33.1013	$33.10	$33.10	$33.10
7 purchase totals =	$811.57		$861.0287	$861.04	$861.00	$861.10