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	$89.98	7.172%	$96.4334	$96.43	$96.45	$96.40
Purchase #2	$248.63	6.400%	$264.5423	$264.54	$264.55	$264.50
Purchase #3	$157.55	13.327%	$178.5467	$178.55	$178.55	$178.50
Purchase #4	$87.99	11.622%	$98.2162	$98.22	$98.20	$98.20
Purchase #5	$82.46	3.789%	$85.5844	$85.58	$85.60	$85.60
Purchase #6	$164.36	7.538%	$176.7495	$176.75	$176.75	$176.70
Purchase #7	$229.42	7.781%	$247.2712	$247.27	$247.25	$247.30
7 purchase totals =	$1,060.39		$1,147.3437	$1,147.34	$1,147.35	$1,147.20