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	$21.85	6.754%	$23.3257	$23.33	$23.35	$23.30
Purchase #2	$39.38	6.427%	$41.911	$41.91	$41.90	$41.90
Purchase #3	$196.84	5.803%	$208.2626	$208.26	$208.25	$208.30
Purchase #4	$128.92	10.751%	$142.7802	$142.78	$142.80	$142.80
Purchase #5	$140.71	11.268%	$156.5652	$156.57	$156.55	$156.60
Purchase #6	$145.26	5.126%	$152.706	$152.71	$152.70	$152.70
Purchase #7	$152.87	7.816%	$164.8183	$164.82	$164.80	$164.80
7 purchase totals =	$825.83		$890.3690	$890.38	$890.35	$890.40