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	$53.86	6.466%	$57.3426	$57.34	$57.35	$57.30
Purchase #2	$64.84	7.228%	$69.5266	$69.53	$69.55	$69.50
Purchase #3	$38.28	5.627%	$40.434	$40.43	$40.45	$40.40
Purchase #4	$22.50	13.757%	$25.5953	$25.60	$25.60	$25.60
Purchase #5	$107.35	10.391%	$118.5047	$118.50	$118.50	$118.50
Purchase #6	$28.34	12.602%	$31.9114	$31.91	$31.90	$31.90
Purchase #7	$61.60	13.300%	$69.7928	$69.79	$69.80	$69.80
7 purchase totals =	$376.77		$413.1074	$413.10	$413.15	$413.00