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	$80.52	11.472%	$89.7573	$89.76	$89.75	$89.80
Purchase #2	$223.73	9.758%	$245.5616	$245.56	$245.55	$245.60
Purchase #3	$243.41	13.598%	$276.5089	$276.51	$276.50	$276.50
Purchase #4	$49.41	8.455%	$53.5876	$53.59	$53.60	$53.60
Purchase #5	$224.54	7.486%	$241.3491	$241.35	$241.35	$241.30
Purchase #6	$168.90	11.864%	$188.9383	$188.94	$188.95	$188.90
Purchase #7	$58.81	11.322%	$65.4685	$65.47	$65.45	$65.50
7 purchase totals =	$1,049.32		$1,161.1713	$1,161.18	$1,161.15	$1,161.20