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	$181.95	7.809%	$196.1585	$196.16	$196.15	$196.20
Purchase #2	$25.48	7.170%	$27.3069	$27.31	$27.30	$27.30
Purchase #3	$161.31	10.491%	$178.233	$178.23	$178.25	$178.20
Purchase #4	$96.61	3.225%	$99.7257	$99.73	$99.75	$99.70
Purchase #5	$248.91	12.688%	$280.4917	$280.49	$280.50	$280.50
Purchase #6	$123.79	9.775%	$135.8905	$135.89	$135.90	$135.90
Purchase #7	$13.83	4.455%	$14.4461	$14.45	$14.45	$14.40
7 purchase totals =	$851.88		$932.2524	$932.26	$932.30	$932.20