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	$186.36	11.769%	$208.2927	$208.29	$208.30	$208.30
Purchase #2	$98.41	4.759%	$103.0933	$103.09	$103.10	$103.10
Purchase #3	$96.71	3.380%	$99.9788	$99.98	$100.00	$100.00
Purchase #4	$219.61	3.663%	$227.6543	$227.65	$227.65	$227.70
Purchase #5	$92.68	9.446%	$101.4346	$101.43	$101.45	$101.40
Purchase #6	$103.66	7.713%	$111.6553	$111.66	$111.65	$111.70
Purchase #7	$83.54	12.172%	$93.7085	$93.71	$93.70	$93.70
7 purchase totals =	$880.97		$945.8175	$945.81	$945.85	$945.90