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	$177.78	8.312%	$192.5571	$192.56	$192.55	$192.60
Purchase #2	$115.38	3.587%	$119.5187	$119.52	$119.50	$119.50
Purchase #3	$235.71	10.740%	$261.0253	$261.03	$261.05	$261.00
Purchase #4	$177.91	11.608%	$198.5618	$198.56	$198.55	$198.60
Purchase #5	$82.50	3.208%	$85.1466	$85.15	$85.15	$85.10
Purchase #6	$33.67	11.219%	$37.4474	$37.45	$37.45	$37.40
Purchase #7	$244.88	11.281%	$272.5049	$272.50	$272.50	$272.50
7 purchase totals =	$1,067.83		$1,166.7618	$1,166.77	$1,166.75	$1,166.70