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	$79.75	7.347%	$85.6092	$85.61	$85.60	$85.60
Purchase #2	$209.77	13.490%	$238.068	$238.07	$238.05	$238.10
Purchase #3	$110.31	4.787%	$115.5905	$115.59	$115.60	$115.60
Purchase #4	$99.99	8.482%	$108.4712	$108.47	$108.45	$108.50
Purchase #5	$79.31	9.464%	$86.8159	$86.82	$86.80	$86.80
Purchase #6	$135.76	3.442%	$140.4329	$140.43	$140.45	$140.40
Purchase #7	$154.94	3.644%	$160.586	$160.59	$160.60	$160.60
7 purchase totals =	$869.83		$935.5737	$935.58	$935.55	$935.60