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	$156.33	9.846%	$171.7223	$171.72	$171.70	$171.70
Purchase #2	$117.80	7.472%	$126.602	$126.60	$126.60	$126.60
Purchase #3	$184.79	3.686%	$191.6014	$191.60	$191.60	$191.60
Purchase #4	$211.54	3.457%	$218.8529	$218.85	$218.85	$218.90
Purchase #5	$39.85	7.182%	$42.712	$42.71	$42.70	$42.70
Purchase #6	$131.32	8.141%	$142.0108	$142.01	$142.00	$142.00
Purchase #7	$44.77	9.529%	$49.0361	$49.04	$49.05	$49.00
7 purchase totals =	$886.40		$942.5375	$942.53	$942.50	$942.50