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	$32.59	5.814%	$34.4848	$34.48	$34.50	$34.50
Purchase #2	$236.56	8.377%	$256.3766	$256.38	$256.40	$256.40
Purchase #3	$160.91	11.711%	$179.7542	$179.75	$179.75	$179.80
Purchase #4	$120.78	6.310%	$128.4012	$128.40	$128.40	$128.40
Purchase #5	$243.53	5.814%	$257.6888	$257.69	$257.70	$257.70
Purchase #6	$98.91	4.657%	$103.5162	$103.52	$103.50	$103.50
Purchase #7	$110.40	12.119%	$123.7794	$123.78	$123.80	$123.80
7 purchase totals =	$1,003.68		$1,084.0012	$1,084.00	$1,084.05	$1,084.10