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	$66.95	11.330%	$74.5354	$74.54	$74.55	$74.50
Purchase #2	$214.79	9.762%	$235.7578	$235.76	$235.75	$235.80
Purchase #3	$53.53	3.626%	$55.471	$55.47	$55.45	$55.50
Purchase #4	$56.41	8.819%	$61.3848	$61.38	$61.40	$61.40
Purchase #5	$226.66	3.807%	$235.2889	$235.29	$235.30	$235.30
Purchase #6	$103.81	5.502%	$109.5216	$109.52	$109.50	$109.50
Purchase #7	$98.41	13.164%	$111.3647	$111.36	$111.35	$111.40
7 purchase totals =	$820.56		$883.3242	$883.32	$883.30	$883.40