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	$142.31	7.428%	$152.8808	$152.88	$152.90	$152.90
Purchase #2	$94.90	4.270%	$98.9522	$98.95	$98.95	$99.00
Purchase #3	$39.67	4.730%	$41.5464	$41.55	$41.55	$41.50
Purchase #4	$139.32	11.230%	$154.9656	$154.97	$154.95	$155.00
Purchase #5	$94.26	6.768%	$100.6395	$100.64	$100.65	$100.60
Purchase #6	$132.47	9.255%	$144.7301	$144.73	$144.75	$144.70
Purchase #7	$240.28	4.814%	$251.8471	$251.85	$251.85	$251.80
7 purchase totals =	$883.21		$945.5617	$945.57	$945.60	$945.50