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	$179.90	3.352%	$185.9302	$185.93	$185.95	$185.90
Purchase #2	$250.83	9.466%	$274.5736	$274.57	$274.55	$274.60
Purchase #3	$92.58	3.547%	$95.8638	$95.86	$95.85	$95.90
Purchase #4	$107.95	4.592%	$112.9071	$112.91	$112.90	$112.90
Purchase #5	$44.42	8.258%	$48.0882	$48.09	$48.10	$48.10
Purchase #6	$60.88	10.671%	$67.3765	$67.38	$67.40	$67.40
Purchase #7	$165.77	10.572%	$183.2952	$183.30	$183.30	$183.30
7 purchase totals =	$902.33		$968.0346	$968.04	$968.05	$968.10