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	$77.60	11.481%	$86.5093	$86.51	$86.50	$86.50
Purchase #2	$133.33	3.351%	$137.7979	$137.80	$137.80	$137.80
Purchase #3	$51.90	4.551%	$54.262	$54.26	$54.25	$54.30
Purchase #4	$147.44	11.483%	$164.3705	$164.37	$164.35	$164.40
Purchase #5	$207.40	10.567%	$229.316	$229.32	$229.30	$229.30
Purchase #6	$233.37	6.500%	$248.5391	$248.54	$248.55	$248.50
Purchase #7	$112.53	11.193%	$125.1255	$125.13	$125.15	$125.10
7 purchase totals =	$963.57		$1,045.9203	$1,045.93	$1,045.90	$1,045.90