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	$147.42	13.300%	$167.0269	$167.03	$167.05	$167.00
Purchase #2	$97.82	13.806%	$111.325	$111.33	$111.35	$111.30
Purchase #3	$91.98	9.837%	$101.0281	$101.03	$101.05	$101.00
Purchase #4	$80.90	10.587%	$89.4649	$89.46	$89.45	$89.50
Purchase #5	$181.64	9.802%	$199.4444	$199.44	$199.45	$199.40
Purchase #6	$67.57	5.577%	$71.3384	$71.34	$71.35	$71.30
Purchase #7	$190.90	7.407%	$205.04	$205.04	$205.05	$205.00
7 purchase totals =	$858.23		$944.6677	$944.67	$944.75	$944.50