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	$166.43	10.108%	$183.2527	$183.25	$183.25	$183.30
Purchase #2	$176.98	6.807%	$189.027	$189.03	$189.05	$189.00
Purchase #3	$150.86	7.813%	$162.6467	$162.65	$162.65	$162.60
Purchase #4	$119.44	11.857%	$133.602	$133.60	$133.60	$133.60
Purchase #5	$198.69	8.654%	$215.8846	$215.88	$215.90	$215.90
Purchase #6	$41.75	11.444%	$46.5279	$46.53	$46.55	$46.50
Purchase #7	$37.54	13.586%	$42.6402	$42.64	$42.65	$42.60
7 purchase totals =	$891.69		$973.5811	$973.58	$973.65	$973.50