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	$184.44	7.644%	$198.5386	$198.54	$198.55	$198.50
Purchase #2	$91.34	6.631%	$97.3968	$97.40	$97.40	$97.40
Purchase #3	$205.26	3.185%	$211.7975	$211.80	$211.80	$211.80
Purchase #4	$142.42	3.855%	$147.9103	$147.91	$147.90	$147.90
Purchase #5	$120.30	6.278%	$127.8524	$127.85	$127.85	$127.90
Purchase #6	$167.45	3.648%	$173.5586	$173.56	$173.55	$173.60
Purchase #7	$216.38	11.754%	$241.8133	$241.81	$241.80	$241.80
7 purchase totals =	$1,127.59		$1,198.8675	$1,198.87	$1,198.85	$1,198.90