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	$91.27	3.638%	$94.5904	$94.59	$94.60	$94.60
Purchase #2	$142.50	4.394%	$148.7615	$148.76	$148.75	$148.80
Purchase #3	$174.78	12.535%	$196.6887	$196.69	$196.70	$196.70
Purchase #4	$209.99	6.475%	$223.5869	$223.59	$223.60	$223.60
Purchase #5	$21.64	6.744%	$23.0994	$23.10	$23.10	$23.10
Purchase #6	$176.38	7.356%	$189.3545	$189.35	$189.35	$189.40
Purchase #7	$123.42	7.164%	$132.2618	$132.26	$132.25	$132.30
7 purchase totals =	$939.98		$1,008.3432	$1,008.34	$1,008.35	$1,008.50