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	$235.78	13.820%	$268.3648	$268.36	$268.35	$268.40
Purchase #2	$117.79	5.615%	$124.4039	$124.40	$124.40	$124.40
Purchase #3	$128.86	13.757%	$146.5873	$146.59	$146.60	$146.60
Purchase #4	$122.73	7.463%	$131.8893	$131.89	$131.90	$131.90
Purchase #5	$41.60	10.718%	$46.0587	$46.06	$46.05	$46.10
Purchase #6	$205.76	3.397%	$212.7497	$212.75	$212.75	$212.70
Purchase #7	$91.96	13.439%	$104.3185	$104.32	$104.30	$104.30
7 purchase totals =	$944.48		$1,034.3722	$1,034.37	$1,034.35	$1,034.40