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	$247.39	9.107%	$269.9198	$269.92	$269.90	$269.90
Purchase #2	$71.41	8.566%	$77.527	$77.53	$77.55	$77.50
Purchase #3	$76.46	9.780%	$83.9378	$83.94	$83.95	$83.90
Purchase #4	$126.81	11.114%	$140.9037	$140.90	$140.90	$140.90
Purchase #5	$69.98	13.673%	$79.5484	$79.55	$79.55	$79.50
Purchase #6	$136.29	10.162%	$150.1398	$150.14	$150.15	$150.10
Purchase #7	$225.32	13.492%	$255.7202	$255.72	$255.70	$255.70
7 purchase totals =	$953.66		$1,057.6967	$1,057.70	$1,057.70	$1,057.50