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	$206.59	11.349%	$230.0359	$230.04	$230.05	$230.00
Purchase #2	$153.79	7.189%	$164.846	$164.85	$164.85	$164.80
Purchase #3	$122.56	7.369%	$131.5914	$131.59	$131.60	$131.60
Purchase #4	$119.91	3.157%	$123.6956	$123.70	$123.70	$123.70
Purchase #5	$165.76	3.838%	$172.1219	$172.12	$172.10	$172.10
Purchase #6	$67.46	5.223%	$70.9834	$70.98	$71.00	$71.00
Purchase #7	$196.64	9.647%	$215.6099	$215.61	$215.60	$215.60
7 purchase totals =	$1,032.71		$1,108.8841	$1,108.89	$1,108.90	$1,108.80