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	$37.69	6.543%	$40.1561	$40.16	$40.15	$40.20
Purchase #2	$174.59	6.515%	$185.9645	$185.96	$185.95	$186.00
Purchase #3	$13.38	10.471%	$14.781	$14.78	$14.80	$14.80
Purchase #4	$82.95	13.631%	$94.2569	$94.26	$94.25	$94.30
Purchase #5	$146.27	13.597%	$166.1583	$166.16	$166.15	$166.20
Purchase #6	$144.87	4.802%	$151.8267	$151.83	$151.85	$151.80
Purchase #7	$171.77	11.477%	$191.484	$191.48	$191.50	$191.50
7 purchase totals =	$771.52		$844.6275	$844.63	$844.65	$844.80