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	$224.48	8.535%	$243.6394	$243.64	$243.65	$243.60
Purchase #2	$245.26	12.276%	$275.3681	$275.37	$275.35	$275.40
Purchase #3	$5.92	8.755%	$6.4383	$6.44	$6.45	$6.40
Purchase #4	$50.55	10.695%	$55.9563	$55.96	$55.95	$56.00
Purchase #5	$53.37	12.165%	$59.8625	$59.86	$59.85	$59.90
Purchase #6	$161.83	10.389%	$178.6425	$178.64	$178.65	$178.60
Purchase #7	$106.93	4.719%	$111.976	$111.98	$112.00	$112.00
7 purchase totals =	$848.34		$931.8831	$931.89	$931.90	$931.90