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	$110.44	3.631%	$114.4501	$114.45	$114.45	$114.50
Purchase #2	$125.44	4.743%	$131.3896	$131.39	$131.40	$131.40
Purchase #3	$85.71	6.644%	$91.4046	$91.40	$91.40	$91.40
Purchase #4	$77.48	4.342%	$80.8442	$80.84	$80.85	$80.80
Purchase #5	$216.42	5.723%	$228.8057	$228.81	$228.80	$228.80
Purchase #6	$232.31	13.218%	$263.0167	$263.02	$263.00	$263.00
Purchase #7	$82.69	4.738%	$86.6079	$86.61	$86.60	$86.60
7 purchase totals =	$930.49		$996.5188	$996.52	$996.50	$996.50