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	$210.80	13.257%	$238.7458	$238.75	$238.75	$238.70
Purchase #2	$164.56	4.649%	$172.2104	$172.21	$172.20	$172.20
Purchase #3	$167.36	13.759%	$190.3871	$190.39	$190.40	$190.40
Purchase #4	$150.82	7.770%	$162.5387	$162.54	$162.55	$162.50
Purchase #5	$219.98	11.329%	$244.9015	$244.90	$244.90	$244.90
Purchase #6	$9.72	5.631%	$10.2673	$10.27	$10.25	$10.30
Purchase #7	$167.61	8.399%	$181.6876	$181.69	$181.70	$181.70
7 purchase totals =	$1,090.85		$1,200.7384	$1,200.75	$1,200.75	$1,200.70