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	$83.42	5.343%	$87.8771	$87.88	$87.90	$87.90
Purchase #2	$240.88	11.821%	$269.3544	$269.35	$269.35	$269.40
Purchase #3	$221.55	9.406%	$242.389	$242.39	$242.40	$242.40
Purchase #4	$222.89	13.536%	$253.0604	$253.06	$253.05	$253.10
Purchase #5	$151.43	11.241%	$168.4522	$168.45	$168.45	$168.50
Purchase #6	$67.37	13.280%	$76.3167	$76.32	$76.30	$76.30
Purchase #7	$63.92	9.237%	$69.8243	$69.82	$69.80	$69.80
7 purchase totals =	$1,051.46		$1,167.2741	$1,167.27	$1,167.25	$1,167.40