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	$187.45	11.582%	$209.1605	$209.16	$209.15	$209.20
Purchase #2	$59.82	12.533%	$67.3172	$67.32	$67.30	$67.30
Purchase #3	$147.67	11.249%	$164.2814	$164.28	$164.30	$164.30
Purchase #4	$91.39	8.673%	$99.3163	$99.32	$99.30	$99.30
Purchase #5	$145.74	11.408%	$162.366	$162.37	$162.35	$162.40
Purchase #6	$70.86	9.605%	$77.6661	$77.67	$77.65	$77.70
Purchase #7	$111.64	5.545%	$117.8304	$117.83	$117.85	$117.80
7 purchase totals =	$814.57		$897.9379	$897.95	$897.90	$898.00