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	$233.84	11.510%	$260.755	$260.76	$260.75	$260.80
Purchase #2	$39.27	3.285%	$40.56	$40.56	$40.55	$40.60
Purchase #3	$216.48	8.527%	$234.9392	$234.94	$234.95	$234.90
Purchase #4	$51.84	11.317%	$57.7067	$57.71	$57.70	$57.70
Purchase #5	$43.95	5.841%	$46.5171	$46.52	$46.50	$46.50
Purchase #6	$147.62	12.139%	$165.5396	$165.54	$165.55	$165.50
Purchase #7	$87.76	12.260%	$98.5194	$98.52	$98.50	$98.50
7 purchase totals =	$820.76		$904.5370	$904.55	$904.50	$904.50