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	$221.68	5.531%	$233.9411	$233.94	$233.95	$233.90
Purchase #2	$41.45	10.832%	$45.9399	$45.94	$45.95	$45.90
Purchase #3	$96.93	8.139%	$104.8191	$104.82	$104.80	$104.80
Purchase #4	$115.32	8.272%	$124.8593	$124.86	$124.85	$124.90
Purchase #5	$76.87	4.165%	$80.0716	$80.07	$80.05	$80.10
Purchase #6	$176.44	8.319%	$191.118	$191.12	$191.10	$191.10
Purchase #7	$210.45	13.389%	$238.6272	$238.63	$238.65	$238.60
7 purchase totals =	$939.14		$1,019.3762	$1,019.38	$1,019.35	$1,019.30