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	$14.34	10.238%	$15.8081	$15.81	$15.80	$15.80
Purchase #2	$229.33	4.495%	$239.6384	$239.64	$239.65	$239.60
Purchase #3	$47.53	10.507%	$52.524	$52.52	$52.50	$52.50
Purchase #4	$119.31	6.760%	$127.3754	$127.38	$127.40	$127.40
Purchase #5	$89.76	3.457%	$92.863	$92.86	$92.85	$92.90
Purchase #6	$57.44	8.872%	$62.5361	$62.54	$62.55	$62.50
Purchase #7	$130.45	8.680%	$141.7731	$141.77	$141.75	$141.80
7 purchase totals =	$688.16		$732.5181	$732.52	$732.50	$732.50