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	$109.73	10.684%	$121.4536	$121.45	$121.45	$121.50
Purchase #2	$245.72	7.339%	$263.7534	$263.75	$263.75	$263.80
Purchase #3	$134.91	13.780%	$153.5006	$153.50	$153.50	$153.50
Purchase #4	$99.82	9.239%	$109.0424	$109.04	$109.05	$109.00
Purchase #5	$136.42	3.505%	$141.2015	$141.20	$141.20	$141.20
Purchase #6	$107.48	3.112%	$110.8248	$110.82	$110.80	$110.80
Purchase #7	$144.78	6.426%	$154.0836	$154.08	$154.10	$154.10
7 purchase totals =	$978.86		$1,053.8599	$1,053.84	$1,053.85	$1,053.90