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	$112.45	10.107%	$123.8153	$123.82	$123.80	$123.80
Purchase #2	$85.53	5.140%	$89.9262	$89.93	$89.95	$89.90
Purchase #3	$199.72	13.722%	$227.1256	$227.13	$227.15	$227.10
Purchase #4	$182.52	8.766%	$198.5197	$198.52	$198.50	$198.50
Purchase #5	$73.46	11.281%	$81.747	$81.75	$81.75	$81.70
Purchase #6	$115.92	10.472%	$128.0591	$128.06	$128.05	$128.10
Purchase #7	$156.93	3.258%	$162.0428	$162.04	$162.05	$162.00
7 purchase totals =	$926.53		$1,011.2357	$1,011.25	$1,011.25	$1,011.10