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	$214.28	12.415%	$240.8829	$240.88	$240.90	$240.90
Purchase #2	$45.79	4.850%	$48.0108	$48.01	$48.00	$48.00
Purchase #3	$216.82	12.690%	$244.3345	$244.33	$244.35	$244.30
Purchase #4	$27.56	3.441%	$28.5083	$28.51	$28.50	$28.50
Purchase #5	$158.32	4.289%	$165.1103	$165.11	$165.10	$165.10
Purchase #6	$10.43	10.440%	$11.5189	$11.52	$11.50	$11.50
Purchase #7	$237.48	10.575%	$262.5935	$262.59	$262.60	$262.60
7 purchase totals =	$910.68		$1,000.9592	$1,000.95	$1,000.95	$1,000.90