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	$212.69	11.317%	$236.7601	$236.76	$236.75	$236.80
Purchase #2	$245.59	4.181%	$255.8581	$255.86	$255.85	$255.90
Purchase #3	$60.98	4.524%	$63.7387	$63.74	$63.75	$63.70
Purchase #4	$55.73	12.729%	$62.8239	$62.82	$62.80	$62.80
Purchase #5	$142.91	11.863%	$159.8634	$159.86	$159.85	$159.90
Purchase #6	$95.66	10.121%	$105.3417	$105.34	$105.35	$105.30
Purchase #7	$124.48	5.469%	$131.2878	$131.29	$131.30	$131.30
7 purchase totals =	$938.04		$1,015.6737	$1,015.67	$1,015.65	$1,015.70