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	$177.34	5.336%	$186.8029	$186.80	$186.80	$186.80
Purchase #2	$72.83	7.834%	$78.5355	$78.54	$78.55	$78.50
Purchase #3	$181.29	9.258%	$198.0738	$198.07	$198.05	$198.10
Purchase #4	$219.95	8.494%	$238.6326	$238.63	$238.65	$238.60
Purchase #5	$201.91	7.551%	$217.1562	$217.16	$217.15	$217.20
Purchase #6	$103.82	8.759%	$112.9136	$112.91	$112.90	$112.90
Purchase #7	$16.50	11.824%	$18.451	$18.45	$18.45	$18.50
7 purchase totals =	$973.64		$1,050.5656	$1,050.56	$1,050.55	$1,050.60