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	$103.75	10.624%	$114.7724	$114.77	$114.75	$114.80
Purchase #2	$210.93	12.227%	$236.7204	$236.72	$236.70	$236.70
Purchase #3	$164.47	11.354%	$183.1439	$183.14	$183.15	$183.10
Purchase #4	$239.64	9.568%	$262.5688	$262.57	$262.55	$262.60
Purchase #5	$94.34	6.754%	$100.7117	$100.71	$100.70	$100.70
Purchase #6	$35.74	8.557%	$38.7983	$38.80	$38.80	$38.80
Purchase #7	$60.72	10.440%	$67.0592	$67.06	$67.05	$67.10
7 purchase totals =	$909.59		$1,003.7747	$1,003.77	$1,003.70	$1,003.80