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	$244.51	8.740%	$265.8802	$265.88	$265.90	$265.90
Purchase #2	$130.98	5.597%	$138.311	$138.31	$138.30	$138.30
Purchase #3	$139.90	6.477%	$148.9613	$148.96	$148.95	$149.00
Purchase #4	$84.41	7.550%	$90.783	$90.78	$90.80	$90.80
Purchase #5	$157.87	4.818%	$165.4762	$165.48	$165.50	$165.50
Purchase #6	$173.97	12.684%	$196.0364	$196.04	$196.05	$196.00
Purchase #7	$168.78	5.731%	$178.4528	$178.45	$178.45	$178.50
7 purchase totals =	$1,100.42		$1,183.9009	$1,183.90	$1,183.95	$1,184.00