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	$103.91	9.840%	$114.1347	$114.13	$114.15	$114.10
Purchase #2	$118.90	13.356%	$134.7803	$134.78	$134.80	$134.80
Purchase #3	$182.88	11.317%	$203.5765	$203.58	$203.60	$203.60
Purchase #4	$151.27	10.800%	$167.6072	$167.61	$167.60	$167.60
Purchase #5	$118.77	6.524%	$126.5186	$126.52	$126.50	$126.50
Purchase #6	$57.73	3.278%	$59.6224	$59.62	$59.60	$59.60
Purchase #7	$175.27	3.313%	$181.0767	$181.08	$181.10	$181.10
7 purchase totals =	$908.73		$987.3164	$987.32	$987.35	$987.30