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	$98.87	12.459%	$111.1882	$111.19	$111.20	$111.20
Purchase #2	$52.42	7.423%	$56.3111	$56.31	$56.30	$56.30
Purchase #3	$128.87	9.835%	$141.5444	$141.54	$141.55	$141.50
Purchase #4	$215.79	12.126%	$241.9567	$241.96	$241.95	$242.00
Purchase #5	$122.34	12.827%	$138.0326	$138.03	$138.05	$138.00
Purchase #6	$233.57	6.310%	$248.3083	$248.31	$248.30	$248.30
Purchase #7	$140.73	12.867%	$158.8377	$158.84	$158.85	$158.80
7 purchase totals =	$992.59		$1,096.1790	$1,096.18	$1,096.20	$1,096.10