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	$40.98	6.463%	$43.6285	$43.63	$43.65	$43.60
Purchase #2	$65.90	9.167%	$71.9411	$71.94	$71.95	$71.90
Purchase #3	$141.67	6.802%	$151.3064	$151.31	$151.30	$151.30
Purchase #4	$79.64	3.498%	$82.4258	$82.43	$82.45	$82.40
Purchase #5	$14.85	11.366%	$16.5379	$16.54	$16.55	$16.50
Purchase #6	$35.95	12.860%	$40.5732	$40.57	$40.55	$40.60
Purchase #7	$168.83	8.216%	$182.7011	$182.70	$182.70	$182.70
7 purchase totals =	$547.82		$589.1140	$589.12	$589.15	$589.00