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	$199.92	4.195%	$208.3066	$208.31	$208.30	$208.30
Purchase #2	$38.48	6.688%	$41.0535	$41.05	$41.05	$41.10
Purchase #3	$27.67	13.571%	$31.4251	$31.43	$31.45	$31.40
Purchase #4	$169.27	6.634%	$180.4994	$180.50	$180.50	$180.50
Purchase #5	$139.64	4.143%	$145.4253	$145.43	$145.45	$145.40
Purchase #6	$84.89	5.550%	$89.6014	$89.60	$89.60	$89.60
Purchase #7	$202.59	11.737%	$226.368	$226.37	$226.35	$226.40
7 purchase totals =	$862.46		$922.6793	$922.69	$922.70	$922.70