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	$63.70	13.627%	$72.3804	$72.38	$72.40	$72.40
Purchase #2	$60.80	3.131%	$62.7036	$62.70	$62.70	$62.70
Purchase #3	$166.36	3.731%	$172.5669	$172.57	$172.55	$172.60
Purchase #4	$55.78	3.216%	$57.5739	$57.57	$57.55	$57.60
Purchase #5	$216.30	4.818%	$226.7213	$226.72	$226.70	$226.70
Purchase #6	$173.44	7.105%	$185.7629	$185.76	$185.75	$185.80
Purchase #7	$144.46	6.618%	$154.0204	$154.02	$154.00	$154.00
7 purchase totals =	$880.84		$931.7294	$931.72	$931.65	$931.80