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	$185.25	6.146%	$196.6355	$196.64	$196.65	$196.60
Purchase #2	$84.56	12.770%	$95.3583	$95.36	$95.35	$95.40
Purchase #3	$229.66	12.526%	$258.4272	$258.43	$258.45	$258.40
Purchase #4	$201.56	10.534%	$222.7923	$222.79	$222.80	$222.80
Purchase #5	$154.27	13.802%	$175.5623	$175.56	$175.55	$175.60
Purchase #6	$142.83	9.796%	$156.8216	$156.82	$156.80	$156.80
Purchase #7	$166.98	3.601%	$172.9929	$172.99	$173.00	$173.00
7 purchase totals =	$1,165.11		$1,278.5901	$1,278.59	$1,278.60	$1,278.60