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	$193.38	4.607%	$202.289	$202.29	$202.30	$202.30
Purchase #2	$9.29	11.753%	$10.3819	$10.38	$10.40	$10.40
Purchase #3	$76.91	7.786%	$82.8982	$82.90	$82.90	$82.90
Purchase #4	$136.32	6.688%	$145.4371	$145.44	$145.45	$145.40
Purchase #5	$93.55	8.443%	$101.4484	$101.45	$101.45	$101.40
Purchase #6	$32.59	13.479%	$36.9828	$36.98	$37.00	$37.00
Purchase #7	$242.52	9.299%	$265.0719	$265.07	$265.05	$265.10
7 purchase totals =	$784.56		$844.5093	$844.51	$844.55	$844.50