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	$54.35	4.247%	$56.6582	$56.66	$56.65	$56.70
Purchase #2	$60.79	11.140%	$67.562	$67.56	$67.55	$67.60
Purchase #3	$203.52	11.393%	$226.707	$226.71	$226.70	$226.70
Purchase #4	$177.83	3.411%	$183.8958	$183.90	$183.90	$183.90
Purchase #5	$78.70	13.757%	$89.5268	$89.53	$89.55	$89.50
Purchase #6	$169.68	11.502%	$189.1966	$189.20	$189.20	$189.20
Purchase #7	$233.25	4.753%	$244.3364	$244.34	$244.35	$244.30
7 purchase totals =	$978.12		$1,057.8828	$1,057.90	$1,057.90	$1,057.90