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	$57.71	10.846%	$63.9692	$63.97	$63.95	$64.00
Purchase #2	$143.91	7.351%	$154.4888	$154.49	$154.50	$154.50
Purchase #3	$162.73	11.696%	$181.7629	$181.76	$181.75	$181.80
Purchase #4	$179.86	9.463%	$196.8802	$196.88	$196.90	$196.90
Purchase #5	$39.68	8.471%	$43.0413	$43.04	$43.05	$43.00
Purchase #6	$28.99	9.360%	$31.7035	$31.70	$31.70	$31.70
Purchase #7	$53.60	11.411%	$59.7163	$59.72	$59.70	$59.70
7 purchase totals =	$666.48		$731.5622	$731.56	$731.55	$731.60