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	$143.68	10.858%	$159.2808	$159.28	$159.30	$159.30
Purchase #2	$203.39	11.757%	$227.3026	$227.30	$227.30	$227.30
Purchase #3	$78.91	9.661%	$86.5335	$86.53	$86.55	$86.50
Purchase #4	$39.27	10.388%	$43.3494	$43.35	$43.35	$43.30
Purchase #5	$98.89	6.663%	$105.479	$105.48	$105.50	$105.50
Purchase #6	$180.62	9.259%	$197.3436	$197.34	$197.35	$197.30
Purchase #7	$239.65	9.760%	$263.0398	$263.04	$263.05	$263.00
7 purchase totals =	$984.41		$1,082.3287	$1,082.32	$1,082.40	$1,082.20