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	$235.97	10.840%	$261.5491	$261.55	$261.55	$261.50
Purchase #2	$152.36	7.685%	$164.0689	$164.07	$164.05	$164.10
Purchase #3	$150.87	13.393%	$171.076	$171.08	$171.10	$171.10
Purchase #4	$188.32	7.765%	$202.943	$202.94	$202.95	$202.90
Purchase #5	$7.25	12.142%	$8.1303	$8.13	$8.15	$8.10
Purchase #6	$185.58	5.855%	$196.4457	$196.45	$196.45	$196.40
Purchase #7	$41.33	12.198%	$46.3714	$46.37	$46.35	$46.40
7 purchase totals =	$961.68		$1,050.5844	$1,050.59	$1,050.60	$1,050.50