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	$35.48	6.512%	$37.7905	$37.79	$37.80	$37.80
Purchase #2	$158.40	6.263%	$168.3206	$168.32	$168.30	$168.30
Purchase #3	$240.98	13.184%	$272.7508	$272.75	$272.75	$272.80
Purchase #4	$200.85	7.554%	$216.0222	$216.02	$216.00	$216.00
Purchase #5	$47.45	10.529%	$52.446	$52.45	$52.45	$52.40
Purchase #6	$131.86	8.218%	$142.6963	$142.70	$142.70	$142.70
Purchase #7	$126.59	12.272%	$142.1251	$142.13	$142.15	$142.10
7 purchase totals =	$941.61		$1,032.1515	$1,032.16	$1,032.15	$1,032.10