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	$175.41	11.858%	$196.2101	$196.21	$196.20	$196.20
Purchase #2	$173.70	4.326%	$181.2143	$181.21	$181.20	$181.20
Purchase #3	$156.30	9.285%	$170.8125	$170.81	$170.80	$170.80
Purchase #4	$35.97	8.196%	$38.9181	$38.92	$38.90	$38.90
Purchase #5	$115.52	9.546%	$126.5475	$126.55	$126.55	$126.50
Purchase #6	$179.84	9.284%	$196.5363	$196.54	$196.55	$196.50
Purchase #7	$56.48	13.756%	$64.2494	$64.25	$64.25	$64.20
7 purchase totals =	$893.22		$974.4882	$974.49	$974.45	$974.30