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	$98.79	5.641%	$104.3627	$104.36	$104.35	$104.40
Purchase #2	$177.27	4.810%	$185.7967	$185.80	$185.80	$185.80
Purchase #3	$175.78	11.559%	$196.0984	$196.10	$196.10	$196.10
Purchase #4	$13.32	4.243%	$13.8852	$13.89	$13.90	$13.90
Purchase #5	$163.74	6.430%	$174.2685	$174.27	$174.25	$174.30
Purchase #6	$76.31	9.460%	$83.5289	$83.53	$83.55	$83.50
Purchase #7	$82.54	4.446%	$86.2097	$86.21	$86.20	$86.20
7 purchase totals =	$787.75		$844.1501	$844.16	$844.15	$844.20