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	$176.27	13.250%	$199.6258	$199.63	$199.65	$199.60
Purchase #2	$181.81	4.274%	$189.5806	$189.58	$189.60	$189.60
Purchase #3	$148.48	11.373%	$165.3666	$165.37	$165.35	$165.40
Purchase #4	$86.59	6.649%	$92.3474	$92.35	$92.35	$92.30
Purchase #5	$57.56	11.615%	$64.2456	$64.25	$64.25	$64.20
Purchase #6	$45.86	3.427%	$47.4316	$47.43	$47.45	$47.40
Purchase #7	$153.94	9.706%	$168.8814	$168.88	$168.90	$168.90
7 purchase totals =	$850.51		$927.4790	$927.49	$927.55	$927.40