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	$105.82	8.658%	$114.9819	$114.98	$115.00	$115.00
Purchase #2	$109.82	8.821%	$119.5072	$119.51	$119.50	$119.50
Purchase #3	$31.98	11.769%	$35.7437	$35.74	$35.75	$35.70
Purchase #4	$134.28	10.261%	$148.0585	$148.06	$148.05	$148.10
Purchase #5	$184.79	3.166%	$190.6405	$190.64	$190.65	$190.60
Purchase #6	$55.93	9.236%	$61.0957	$61.10	$61.10	$61.10
Purchase #7	$48.76	7.723%	$52.5257	$52.53	$52.55	$52.50
7 purchase totals =	$671.38		$722.5532	$722.56	$722.60	$722.50