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	$187.48	13.485%	$212.7617	$212.76	$212.75	$212.80
Purchase #2	$124.70	3.799%	$129.4374	$129.44	$129.45	$129.40
Purchase #3	$85.43	4.678%	$89.4264	$89.43	$89.45	$89.40
Purchase #4	$106.59	11.210%	$118.5387	$118.54	$118.55	$118.50
Purchase #5	$116.33	6.475%	$123.8624	$123.86	$123.85	$123.90
Purchase #6	$112.29	5.566%	$118.5401	$118.54	$118.55	$118.50
Purchase #7	$214.96	9.360%	$235.0803	$235.08	$235.10	$235.10
7 purchase totals =	$947.78		$1,027.6470	$1,027.65	$1,027.70	$1,027.60