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	$78.40	9.404%	$85.7727	$85.77	$85.75	$85.80
Purchase #2	$168.35	8.616%	$182.855	$182.86	$182.85	$182.90
Purchase #3	$124.38	12.489%	$139.9138	$139.91	$139.90	$139.90
Purchase #4	$111.31	6.592%	$118.6476	$118.65	$118.65	$118.60
Purchase #5	$203.81	13.590%	$231.5078	$231.51	$231.50	$231.50
Purchase #6	$51.39	10.755%	$56.917	$56.92	$56.90	$56.90
Purchase #7	$206.79	4.841%	$216.8007	$216.80	$216.80	$216.80
7 purchase totals =	$944.43		$1,032.4146	$1,032.42	$1,032.35	$1,032.40