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	$215.31	9.407%	$235.5642	$235.56	$235.55	$235.60
Purchase #2	$191.73	3.539%	$198.5153	$198.52	$198.50	$198.50
Purchase #3	$37.81	6.728%	$40.3539	$40.35	$40.35	$40.40
Purchase #4	$55.92	13.659%	$63.5581	$63.56	$63.55	$63.60
Purchase #5	$248.38	11.480%	$276.894	$276.89	$276.90	$276.90
Purchase #6	$111.41	9.159%	$121.614	$121.61	$121.60	$121.60
Purchase #7	$138.39	7.560%	$148.8523	$148.85	$148.85	$148.90
7 purchase totals =	$998.95		$1,085.3518	$1,085.34	$1,085.30	$1,085.50