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	$191.73	7.157%	$205.4521	$205.45	$205.45	$205.50
Purchase #2	$196.36	11.178%	$218.3091	$218.31	$218.30	$218.30
Purchase #3	$248.63	12.666%	$280.1215	$280.12	$280.10	$280.10
Purchase #4	$241.55	13.578%	$274.3477	$274.35	$274.35	$274.30
Purchase #5	$81.80	9.166%	$89.2978	$89.30	$89.30	$89.30
Purchase #6	$168.89	9.147%	$184.3384	$184.34	$184.35	$184.30
Purchase #7	$234.32	9.464%	$256.496	$256.50	$256.50	$256.50
7 purchase totals =	$1,363.28		$1,508.3626	$1,508.37	$1,508.35	$1,508.30