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	$152.61	7.516%	$164.0802	$164.08	$164.10	$164.10
Purchase #2	$51.31	11.798%	$57.3636	$57.36	$57.35	$57.40
Purchase #3	$233.60	13.791%	$265.8158	$265.82	$265.80	$265.80
Purchase #4	$248.63	12.789%	$280.4273	$280.43	$280.45	$280.40
Purchase #5	$24.87	10.218%	$27.4112	$27.41	$27.40	$27.40
Purchase #6	$85.67	8.315%	$92.7935	$92.79	$92.80	$92.80
Purchase #7	$221.79	8.345%	$240.2984	$240.30	$240.30	$240.30
7 purchase totals =	$1,018.48		$1,128.1900	$1,128.19	$1,128.20	$1,128.20