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	$181.65	6.718%	$193.8532	$193.85	$193.85	$193.90
Purchase #2	$191.35	12.874%	$215.9844	$215.98	$216.00	$216.00
Purchase #3	$76.54	6.685%	$81.6567	$81.66	$81.65	$81.70
Purchase #4	$215.31	12.670%	$242.5898	$242.59	$242.60	$242.60
Purchase #5	$230.99	5.555%	$243.8215	$243.82	$243.80	$243.80
Purchase #6	$113.44	12.185%	$127.2627	$127.26	$127.25	$127.30
Purchase #7	$86.93	5.343%	$91.5747	$91.57	$91.55	$91.60
7 purchase totals =	$1,096.21		$1,196.7430	$1,196.73	$1,196.70	$1,196.90