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	$111.53	12.337%	$125.2895	$125.29	$125.30	$125.30
Purchase #2	$128.86	11.459%	$143.6261	$143.63	$143.65	$143.60
Purchase #3	$144.56	12.805%	$163.0709	$163.07	$163.05	$163.10
Purchase #4	$12.47	11.455%	$13.8984	$13.90	$13.90	$13.90
Purchase #5	$92.69	12.813%	$104.5664	$104.57	$104.55	$104.60
Purchase #6	$82.56	4.356%	$86.1563	$86.16	$86.15	$86.20
Purchase #7	$61.51	10.348%	$67.8751	$67.88	$67.90	$67.90
7 purchase totals =	$634.18		$704.4827	$704.50	$704.50	$704.60