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	$171.63	9.145%	$187.3256	$187.33	$187.35	$187.30
Purchase #2	$19.93	9.111%	$21.7458	$21.75	$21.75	$21.70
Purchase #3	$133.97	6.306%	$142.4181	$142.42	$142.40	$142.40
Purchase #4	$136.53	4.416%	$142.5592	$142.56	$142.55	$142.60
Purchase #5	$43.27	11.565%	$48.2742	$48.27	$48.25	$48.30
Purchase #6	$232.72	13.265%	$263.5903	$263.59	$263.60	$263.60
Purchase #7	$194.93	9.230%	$212.922	$212.92	$212.90	$212.90
7 purchase totals =	$932.98		$1,018.8352	$1,018.84	$1,018.80	$1,018.80