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	$96.30	4.803%	$100.9253	$100.93	$100.95	$100.90
Purchase #2	$154.84	9.184%	$169.0605	$169.06	$169.05	$169.10
Purchase #3	$150.89	11.363%	$168.0356	$168.04	$168.05	$168.00
Purchase #4	$77.89	3.756%	$80.8155	$80.82	$80.80	$80.80
Purchase #5	$155.64	7.468%	$167.2632	$167.26	$167.25	$167.30
Purchase #6	$182.65	4.488%	$190.8473	$190.85	$190.85	$190.80
Purchase #7	$156.34	4.326%	$163.1033	$163.10	$163.10	$163.10
7 purchase totals =	$974.55		$1,040.0507	$1,040.06	$1,040.05	$1,040.00