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	$170.33	5.624%	$179.9094	$179.91	$179.90	$179.90
Purchase #2	$174.25	6.231%	$185.1075	$185.11	$185.10	$185.10
Purchase #3	$96.42	5.657%	$101.8745	$101.87	$101.85	$101.90
Purchase #4	$215.74	10.757%	$238.9472	$238.95	$238.95	$238.90
Purchase #5	$94.60	10.862%	$104.8755	$104.88	$104.90	$104.90
Purchase #6	$145.82	12.654%	$164.2721	$164.27	$164.25	$164.30
Purchase #7	$95.70	12.797%	$107.9467	$107.95	$107.95	$107.90
7 purchase totals =	$992.86		$1,082.9329	$1,082.94	$1,082.90	$1,082.90