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	$53.94	9.681%	$59.1619	$59.16	$59.15	$59.20
Purchase #2	$75.46	11.301%	$83.9877	$83.99	$84.00	$84.00
Purchase #3	$244.76	6.185%	$259.8984	$259.90	$259.90	$259.90
Purchase #4	$180.74	3.748%	$187.5141	$187.51	$187.50	$187.50
Purchase #5	$54.53	8.772%	$59.3134	$59.31	$59.30	$59.30
Purchase #6	$102.59	5.826%	$108.5669	$108.57	$108.55	$108.60
Purchase #7	$36.83	8.165%	$39.8372	$39.84	$39.85	$39.80
7 purchase totals =	$748.85		$798.2796	$798.28	$798.25	$798.30