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	$183.64	4.799%	$192.4529	$192.45	$192.45	$192.50
Purchase #2	$183.35	4.504%	$191.6081	$191.61	$191.60	$191.60
Purchase #3	$107.99	9.769%	$118.5395	$118.54	$118.55	$118.50
Purchase #4	$75.42	13.372%	$85.5052	$85.51	$85.50	$85.50
Purchase #5	$36.53	13.839%	$41.5854	$41.59	$41.60	$41.60
Purchase #6	$16.91	11.113%	$18.7892	$18.79	$18.80	$18.80
Purchase #7	$62.94	10.623%	$69.6261	$69.63	$69.65	$69.60
7 purchase totals =	$666.78		$718.1064	$718.12	$718.15	$718.10