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	$82.98	10.374%	$91.5883	$91.59	$91.60	$91.60
Purchase #2	$191.57	3.394%	$198.0719	$198.07	$198.05	$198.10
Purchase #3	$132.63	6.628%	$141.4207	$141.42	$141.40	$141.40
Purchase #4	$214.66	3.792%	$222.7999	$222.80	$222.80	$222.80
Purchase #5	$100.88	5.398%	$106.3255	$106.33	$106.35	$106.30
Purchase #6	$130.38	12.540%	$146.7297	$146.73	$146.75	$146.70
Purchase #7	$97.71	5.294%	$102.8828	$102.88	$102.90	$102.90
7 purchase totals =	$950.81		$1,009.8188	$1,009.82	$1,009.85	$1,009.80