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	$136.61	10.154%	$150.4814	$150.48	$150.50	$150.50
Purchase #2	$149.73	6.620%	$159.6421	$159.64	$159.65	$159.60
Purchase #3	$92.53	6.639%	$98.6731	$98.67	$98.65	$98.70
Purchase #4	$89.81	12.327%	$100.8809	$100.88	$100.90	$100.90
Purchase #5	$175.72	3.582%	$182.0143	$182.01	$182.00	$182.00
Purchase #6	$217.82	7.116%	$233.3201	$233.32	$233.30	$233.30
Purchase #7	$176.87	10.230%	$194.9638	$194.96	$194.95	$195.00
7 purchase totals =	$1,039.09		$1,119.9757	$1,119.96	$1,119.95	$1,120.00