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	$147.36	8.326%	$159.6292	$159.63	$159.65	$159.60
Purchase #2	$97.27	8.144%	$105.1917	$105.19	$105.20	$105.20
Purchase #3	$132.74	6.524%	$141.4	$141.40	$141.40	$141.40
Purchase #4	$42.78	10.729%	$47.3699	$47.37	$47.35	$47.40
Purchase #5	$198.35	5.259%	$208.7812	$208.78	$208.80	$208.80
Purchase #6	$151.98	8.720%	$165.2327	$165.23	$165.25	$165.20
Purchase #7	$182.84	3.292%	$188.8591	$188.86	$188.85	$188.90
7 purchase totals =	$953.32		$1,016.4638	$1,016.46	$1,016.50	$1,016.50