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	$169.50	6.700%	$180.8565	$180.86	$180.85	$180.90
Purchase #2	$143.65	6.293%	$152.6899	$152.69	$152.70	$152.70
Purchase #3	$29.39	4.633%	$30.7516	$30.75	$30.75	$30.80
Purchase #4	$121.82	5.274%	$128.2448	$128.24	$128.25	$128.20
Purchase #5	$148.34	8.104%	$160.3615	$160.36	$160.35	$160.40
Purchase #6	$81.94	12.408%	$92.1071	$92.11	$92.10	$92.10
Purchase #7	$246.63	11.443%	$274.8519	$274.85	$274.85	$274.90
7 purchase totals =	$941.27		$1,019.8633	$1,019.86	$1,019.85	$1,020.00