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	$108.51	13.297%	$122.9386	$122.94	$122.95	$122.90
Purchase #2	$89.53	7.140%	$95.9224	$95.92	$95.90	$95.90
Purchase #3	$162.55	3.699%	$168.5627	$168.56	$168.55	$168.60
Purchase #4	$240.71	10.116%	$265.0602	$265.06	$265.05	$265.10
Purchase #5	$48.96	9.583%	$53.6518	$53.65	$53.65	$53.70
Purchase #6	$136.27	13.673%	$154.9022	$154.90	$154.90	$154.90
Purchase #7	$190.82	7.779%	$205.6639	$205.66	$205.65	$205.70
7 purchase totals =	$977.35		$1,066.7018	$1,066.69	$1,066.65	$1,066.80