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	$119.27	10.185%	$131.4176	$131.42	$131.40	$131.40
Purchase #2	$204.81	10.640%	$226.6018	$226.60	$226.60	$226.60
Purchase #3	$48.75	11.659%	$54.4338	$54.43	$54.45	$54.40
Purchase #4	$237.39	4.865%	$248.939	$248.94	$248.95	$248.90
Purchase #5	$164.37	12.472%	$184.8702	$184.87	$184.85	$184.90
Purchase #6	$133.92	4.772%	$140.3107	$140.31	$140.30	$140.30
Purchase #7	$108.60	9.837%	$119.283	$119.28	$119.30	$119.30
7 purchase totals =	$1,017.11		$1,105.8561	$1,105.85	$1,105.85	$1,105.80