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	$219.33	12.822%	$247.4525	$247.45	$247.45	$247.50
Purchase #2	$244.59	8.578%	$265.5709	$265.57	$265.55	$265.60
Purchase #3	$136.40	3.223%	$140.7962	$140.80	$140.80	$140.80
Purchase #4	$181.52	8.426%	$196.8149	$196.81	$196.80	$196.80
Purchase #5	$155.80	10.760%	$172.5641	$172.56	$172.55	$172.60
Purchase #6	$58.84	6.464%	$62.6434	$62.64	$62.65	$62.60
Purchase #7	$85.69	7.734%	$92.3173	$92.32	$92.30	$92.30
7 purchase totals =	$1,082.17		$1,178.1593	$1,178.15	$1,178.10	$1,178.20