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	$154.85	8.699%	$168.3204	$168.32	$168.30	$168.30
Purchase #2	$35.86	11.315%	$39.9176	$39.92	$39.90	$39.90
Purchase #3	$29.80	7.145%	$31.9292	$31.93	$31.95	$31.90
Purchase #4	$247.89	3.206%	$255.8374	$255.84	$255.85	$255.80
Purchase #5	$245.76	9.516%	$269.1465	$269.15	$269.15	$269.10
Purchase #6	$40.68	7.117%	$43.5752	$43.58	$43.60	$43.60
Purchase #7	$117.58	13.643%	$133.6214	$133.62	$133.60	$133.60
7 purchase totals =	$872.42		$942.3477	$942.36	$942.35	$942.20