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	$198.48	3.863%	$206.1473	$206.15	$206.15	$206.10
Purchase #2	$176.33	11.369%	$196.377	$196.38	$196.40	$196.40
Purchase #3	$45.36	6.837%	$48.4613	$48.46	$48.45	$48.50
Purchase #4	$121.38	3.671%	$125.8359	$125.84	$125.85	$125.80
Purchase #5	$26.83	3.508%	$27.7712	$27.77	$27.75	$27.80
Purchase #6	$247.76	6.693%	$264.3426	$264.34	$264.35	$264.30
Purchase #7	$183.50	3.234%	$189.4344	$189.43	$189.45	$189.40
7 purchase totals =	$999.64		$1,058.3697	$1,058.37	$1,058.40	$1,058.30