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	$110.65	5.777%	$117.0423	$117.04	$117.05	$117.00
Purchase #2	$44.78	4.829%	$46.9424	$46.94	$46.95	$46.90
Purchase #3	$78.63	4.678%	$82.3083	$82.31	$82.30	$82.30
Purchase #4	$30.55	9.228%	$33.3692	$33.37	$33.35	$33.40
Purchase #5	$187.65	12.278%	$210.6897	$210.69	$210.70	$210.70
Purchase #6	$95.54	4.572%	$99.9081	$99.91	$99.90	$99.90
Purchase #7	$245.86	3.236%	$253.816	$253.82	$253.80	$253.80
7 purchase totals =	$793.66		$844.0760	$844.08	$844.05	$844.00