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	$10.79	5.841%	$11.4202	$11.42	$11.40	$11.40
Purchase #2	$82.59	4.603%	$86.3916	$86.39	$86.40	$86.40
Purchase #3	$93.89	12.740%	$105.8516	$105.85	$105.85	$105.90
Purchase #4	$188.36	13.259%	$213.3347	$213.33	$213.35	$213.30
Purchase #5	$246.89	7.258%	$264.8093	$264.81	$264.80	$264.80
Purchase #6	$214.52	7.593%	$230.8085	$230.81	$230.80	$230.80
Purchase #7	$113.58	4.319%	$118.4855	$118.49	$118.50	$118.50
7 purchase totals =	$950.62		$1,031.1014	$1,031.10	$1,031.10	$1,031.10