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	$199.39	10.278%	$219.8833	$219.88	$219.90	$219.90
Purchase #2	$186.59	4.647%	$195.2608	$195.26	$195.25	$195.30
Purchase #3	$116.32	13.112%	$131.5719	$131.57	$131.55	$131.60
Purchase #4	$111.49	10.633%	$123.3447	$123.34	$123.35	$123.30
Purchase #5	$101.75	10.128%	$112.0552	$112.06	$112.05	$112.10
Purchase #6	$126.50	3.766%	$131.264	$131.26	$131.25	$131.30
Purchase #7	$56.30	11.542%	$62.7981	$62.80	$62.80	$62.80
7 purchase totals =	$898.34		$976.1780	$976.17	$976.15	$976.30