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	$162.30	6.312%	$172.5444	$172.54	$172.55	$172.50
Purchase #2	$189.92	10.726%	$210.2908	$210.29	$210.30	$210.30
Purchase #3	$156.40	12.192%	$175.4683	$175.47	$175.45	$175.50
Purchase #4	$188.31	4.857%	$197.4562	$197.46	$197.45	$197.50
Purchase #5	$172.44	13.745%	$196.1419	$196.14	$196.15	$196.10
Purchase #6	$109.99	8.399%	$119.2281	$119.23	$119.25	$119.20
Purchase #7	$133.81	3.768%	$138.852	$138.85	$138.85	$138.90
7 purchase totals =	$1,113.17		$1,209.9817	$1,209.98	$1,210.00	$1,210.00