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	$49.30	5.851%	$52.1845	$52.18	$52.20	$52.20
Purchase #2	$167.58	8.542%	$181.8947	$181.89	$181.90	$181.90
Purchase #3	$203.45	13.664%	$231.2494	$231.25	$231.25	$231.20
Purchase #4	$73.49	12.837%	$82.9239	$82.92	$82.90	$82.90
Purchase #5	$191.90	6.636%	$204.6345	$204.63	$204.65	$204.60
Purchase #6	$95.91	7.420%	$103.0265	$103.03	$103.05	$103.00
Purchase #7	$230.40	8.184%	$249.2559	$249.26	$249.25	$249.30
7 purchase totals =	$1,012.03		$1,105.1694	$1,105.16	$1,105.20	$1,105.10