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	$200.60	9.362%	$219.3802	$219.38	$219.40	$219.40
Purchase #2	$89.88	9.590%	$98.4995	$98.50	$98.50	$98.50
Purchase #3	$190.55	6.153%	$202.2745	$202.27	$202.25	$202.30
Purchase #4	$175.27	9.459%	$191.8488	$191.85	$191.85	$191.80
Purchase #5	$156.54	9.843%	$171.9482	$171.95	$171.95	$171.90
Purchase #6	$13.89	9.747%	$15.2439	$15.24	$15.25	$15.20
Purchase #7	$154.44	9.286%	$168.7813	$168.78	$168.80	$168.80
7 purchase totals =	$981.17		$1,067.9764	$1,067.97	$1,068.00	$1,067.90