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	$41.52	13.685%	$47.202	$47.20	$47.20	$47.20
Purchase #2	$175.66	9.165%	$191.7592	$191.76	$191.75	$191.80
Purchase #3	$203.97	9.768%	$223.8938	$223.89	$223.90	$223.90
Purchase #4	$50.85	6.244%	$54.0251	$54.03	$54.05	$54.00
Purchase #5	$223.32	8.307%	$241.8712	$241.87	$241.85	$241.90
Purchase #6	$39.35	11.472%	$43.8642	$43.86	$43.85	$43.90
Purchase #7	$100.33	4.589%	$104.9341	$104.93	$104.95	$104.90
7 purchase totals =	$835.00		$907.5496	$907.54	$907.55	$907.60